Haruhi Suzumiya/WMG/WMG

Haruhi created the series because of her crush on Kyon.
The first episode is an example of her writing quality and superiority complex. On the first day of high school, she was so stricken by the appearance of Kyon in her life that she decided to go home and write furiously about her future high school escapades. She would be the confident Mary Sue character in charge of everyone and avatar of the god of that universe, the real Haruhi (who is likely nothing like she is in real life, or named Haruhi for that matter); Kyon would be The Lancer of her heroes and the only man that can reach her (in a metaphysical sense); and the other three are characters Haruhi previously made up when she wished for aliens, time travelers, and espers to come hang out with her to play on all the anime tropes. The whole story is just Haruhi playing god with her entourage of role-playing characters and her secret crush. She, no doubt, wrote from Kyon's point-of-view in a fantastic delusion of him slowly being overcome over his love for her and kept adding on to is as she realized doesn't even know the real Kyon's name, let alone his real feelings for Haruhi should she finally reveal her epic of a love letter. So, the shut-in Haruhi continues living her god-like life as a writer. No doubt the story was sold to Nagaru Tanigawa, who continued on with the now completely fictional Haruhi and friends while the real Haruhi, weight lifted from her shoulders, enjoys a quiet life with the real Kyon, knowing she warped reality just enough to catch him.

Haruhi likes Anything That Moves
well when she said that she liked aliens, i thought of non-humanoid aliens

Haruhi is Haru...uh...wait...
...uh...I mean...something.

Haruhi, and all IDE's are just regular beings...
...From higher dimensional existences, Haruhi probably being greater than 100+10D

Haruhi shut away her powers to keep from going insane
After being Omnipotent for long enough, she ran out of things to do. Once she had all the power and could do anything, life lost it's purpose. This is probably what happened to AM in I Have No Mouth, and I Must Scream, as well as a what a few characters in Code Geass feared from their immortality. I also remember a few obscure sci-fi novels by Robert Metzger where bubble universes the size of our solar system with accelerated time are created. After about 500 years, someone takes control of the universe, does everything possible with it, and goes crazy trying to find a way out. She made her powers subconscious and rejoined the world so her life had purpose again.

Haruhi Godhood is dependent on her ignorance of it.
The moment she actually becomes aware of it, she'll lose all of it.

While Haruhi isn't actually God, her father is.
She can be seen reaching for his hand in the intro. He is also responsible for all three of the organizations looking after her, as his way of keeping tabs on her.
 * Also according to Kyon one would have to be the Buddha or Jesus Christ to handle her powers, and he also makes it clear that he won't let anyone else have her powers.

Haruhi knows about her powers and everyone's identity.
The truth is that Haruhi likes the Masquerade as much as any other trope. As such, she enjoys seeing them all scramble in an attempt to keep the "secret" from her.
 * We know for a fact that Haruhi causes things to happen when she wants things to happen, but where do we get the idea that she doesn't know about this power? It is really just Itsuki's guess. The fact that no one can tell her about her powers for fear of what would happen if she knew, means that no one can ask her whether she knows about her powers. Our heroes hide the things she does from her so effectively that we never get a chance to see how surprised she would be if she discovered them.
 * We know she doesn't know of her powers because, at the beginning of the story at least, she never mentions having powers. Considering she acted like the world revolved around her, the fact that she never reminded anyone that that was true meant she didn't know.
 * Along with that, she pretends to not know about them; fearing that deliberately acting would cause either a catastrophic epic of plot advancement, or her losing most of her importance and power as the central character.
 * How about Haruhi is doing the Wounded Gazelle Warcry? "Help, I'm stuck with godly powers so you team of unlikely heroes have to save everything!" (This could easily apply to any member of the SOSB, including Kyon.)
 * Alternately, she's waiting for Kyon to tell her the truth. She knows she likes him, and he her, but she doesn't want to be in a relationship if he's going to be dishonest. If she ever admits to knowing, he'll never have the opportunity to tell, and she'll never find out if he really would.

Haruhi's obliviousness of her abilities is a survival mechanism.
If everything a human being thought became true, it wouldn't take long (a few minutes if lucky) before one thinks oneself out of existence. Our neurology cannot process a negative. You can't not think of something without thinking of it first. Example: Right now, try to not think about yourself vanishing forever. Of the infinite Alternate Universe where Haruhi is a Reality Warper, only the ones where Haruhi doesn't think about this exist by process of elimination.

Haruhi is the only person who wouldn't transform into A God Am I
This is something I thought about some time ago. We all know that especially Haruhi would be dangerous if she knew about her powers. It is only natural for a human with godlike powers to become corrupted and use the universe as a playground for amusement and whatsoever. Now what if Haruhi is actually the one human who cannot be corrupted with godlike powers, at least not to the point of A God Am I.

Everything in the show takes place inside Haruhi's head.
The revelation at the baseball game about exactly how far from being the center of the universe she is shattered her mind. She's living out a fantasy of Espers, time travelers, aliens, and handsome love interests, all constructed to put her right back where she thought she was: At the center of everything. Everything in the show takes place in Haruhi's writing

Haruhi has been told that Kyon has the same powers he was told she has.
The other three brigade members have been deceiving both of them. Tsuruya may or may not know this. It's possible that one and only one of them actually does have godlike powers, or that both do, or that neither does, and there's another cause for the madness, which may or may not be.
 * The responsible is Tsuruya, obviously. She must be hiding something.

Kyon's sister's name is actually "Imouto."
Haruhi calls her "Imouto-chan" in the island episode, and Mikuru later calls her "Imouto-san". Maybe it's not just a stand-in title, but her actual given name.
 * Relatedly, Tsuruya's name is actually "San". No one ever uses a different honourific when they're talking about her, do they?
 * Yes they do, Haruhi calls her "Tsuru-chan" at the latter's house in s2e23 when she suggest the drink spiking.
 * Nope. In the English dub, she's just called 'little sister'.
 * Don't think that really applies here.
 * "Imouto" literally means "little sister." This appears to be the only name she is ever given; in fact, her Character Song album's title is "Kyon's Sister," while the others have their full names. (Except Kyon of course.)

Haruhi's powers are a result of an error in Earth's programming.
Due to a glitch in the system, Haruhi was accidentally granted administrator privileges over the program to find The Ultimate Question Of Life The Universe And Everything. The rest of the SOS Brigade's (and particularly Yuki's) jobs are to make sure the program turns out how it's supposed to. Won't they get a rude shock?
 * She discovered both the question and the answer, destroying the Universe and recreating it to be even more weirder, three years ago.

Haruhi is Eris/Discordia...
The mad, trickster goddess of chaos in the Greek/Roman (respectively) pantheons. All the other characters therefore correspond to some other deities.
 * More accurately, she is Eris of Discordian belief, rather than original Greek mythology. More benevolent (sort of) and explicitly the creator of the Universe, rather than just a minor deity. Makes you wonder if Aneris is going to show up, at some point (probably not, considering that she's effectively an incarnation of nonexistence).
 * Not necessarily; just like Eris and chaos, Aneris and order have creative and destructive sides. That said, Kyon is Aneris, or at least her "creative order" aspect. Sort of an anti-Greyface figure, since Greyface was the perfect figure of destructive order. He's the perfect compliment to Haruhi's overwhelmingly creative chaos.
 * Surely Sasaki is Aneris?
 * At an offhand guess:
 * Yuki = Athena/Minerva. Goddess of wisdom, innovation, and warfare, and quite likely the most level-headed Olympian. Fits with Yuki's nature, goals, and affinity for real-time strategy games (and magical girl powers).
 * Mikuru = Hestia/Vesta. Goddess of the hearth and domesticity (Mikuru does enjoy her maid job). Aphrodite/Venus is another possibility, but is usually presented as more assertive.
 * Laughing Aphrodite? Clearly Tsuruya.
 * Itsuki = Apollo. God of wisdom, masculine beauty, and light. Itsuki enjoys philosophy and deduction (at least as applied to Haruhi or mystery games), is very pretty, and turns into a ball of light.
 * Finally, Kyon is not a god, but the latest in the long tradition of hapless mortals accosted by the gods to be a Hero and/or one-night stand. Come to think of it, in the climax of Season 1, he was pretty much both simultaneously, in a PG, socially-appropriate sort of way.
 * Or Kyon is a demigod. I don't know my mythology completely, but weren't pretty much all the Greek heroes this way? He's the latest Heracles, but he doesn't know it yet.
 * Not necessarily. A lot of the ancient heroes were demigods, but just as many were simply mortals who were that badass. Most of the heroes at Troy were mortal, with Achilles being a notable exception.

Alternatively, if Kyon is god, then Haruhi is the "slider".
Let's just face it, we are going to see a "slider" eventually.

Haruhi is a hermaphrodite.
As the old joke goes, "God is neither black nor white. God is neither male nor female. God is neither gay nor straight. Therefore, God is Michael Jackson." However, Haruhi is neither black nor white. She is neither gay nor straight. She is God. Therefore, she is neither male nor female, i.e., a hermaphrodite. (Although about 10,000 Doujinshi artists would try to prove me wrong...)
 * And 10,000 more will try to prove you right.
 * I can do you better. Kyon and Haruhi are male and female aspects of the same being.
 * Does that mean Kyon is bi?
 * Well, considering that Haruhi only shows attraction to Kyon, it just means that he's gay for himself.
 * Haruhi wants to screw herself.
 * It would also explain Koizumi's existence as the "gay option" if you subscribe to the "Kyon is the god" theory.
 * ...Did you just prove that Haruhi is Michael Jackson?

Haruhi is Sakaki's split personality
Haruhi was created by Sakaki's unconscious desires for the supernatural. This could explain many things: Sakaki's team says that Haruhi receiving her powers was a mistake. Haruhi, when seeing Kyon with Sakaki, suffers "not simple jealousy, but a more primitive emotion" according to Koizumi (she fears her own death). Also, it explains the capability that Sakaki has to take over Haruhi's powers. This could be also confirmed by the title of the book: "The Dissociation of Suzumiya Haruhi". It would be worth asking: Why doesn't Kyon EVER meet Haruhi's parents, or even go to her house? Because she DOESN'T have a house! When she has had enough fun with the SOS brigade, she simply disappears.
 * Or possibly visa-versa.

Haruhi created or is otherwise messing around with (Insert Random Fictional Universe Here)
Haruhi is God, so why not? Much like the multiple interpretations and ramifications of the events of Neon Genesis Evangelion, Haruhi's omnipotence creates a very large if not infinitely large dart board to toss Wild Mass Guess darts at; therefore, any theory concerning any fictional universe stating that said universe is created by or is otherwise involved with Haruhi is valid.
 * More importantly, Haruhi created or is otherwise messing around with TV Tropes.
 * Well, duh.
 * So everyone watch what you say and don't give her ideas.
 * Alternatively, Haruhi is TV Tropes personified. When you edit an article, you edit her mind, therefore editing reality. Fortunately, most of TV Tropes describes fiction, so unless somebody starts editing the Real Life pages with cataclysmic disasters, we should be safe.
 * Or did the cataclysmic disastsers happen because they were added to the wiki? Or other things, for that matter? If I really wanted to screw with everyone's minds, I could say that if I edit "Obama becomes first black president" on the real life pages, it will happen, changing history and everyone's memories to belive that it's true. you could argue that it is already true and it's obvious, but do you remember it because it happened or becasue someone added it to the wiki?

Haruhi is a 5th dimension imp
The series ends when she says Ihurah Ayimuzus and is transported back to her home.
 * Or something like "Hiruha Yamizusu" if you're going with Japanese letter-syllables instead of English letters.
 * Did you honestly believe that a 5th-dimensional sorceror would resemble a Japanese schoolgirl with a yellow hairband?
 * Why not?

Kyonko and Haruki are a reshuffling of the KyonHaruhi manifestations
Kyonko looks like Haruhi, and Haruki looks like Kyon. Despite supposedly being Alternate Universe versions of the originals; their personalities have curious differences. One could argue this is just evidence of the pervasiveness of gender expectations on personality...but if both Kyon and Haruhi are Avatars of gods; it's possible they decided to trade more pieces than just gender.
 * Yes, this is Wild Mass Guessing of the solely fan-created Alternate Universe.
 * That just means they look alike. Which, of course, allows the "Kyon and Haruhi are two sides of the same coin" a little more possibility.
 * I think it's more fair to say that Kyonko and Haruki/Haruhiko are just often traced over or drawn off of Haruhi and Kyon than there being any in-universe resemblance. There are just as many pics where Kyonko looks nothing like Haruhi aside from being a generically cute brown-haired girl.

Haruhi will discover her true nature on or not long before December 21, 2012. What she did on 7/7/07 will pale next to what will happen on that day.
12/21/2012 is a couple months into two-thirds of the way through Kyon and Haruhi's last year of high school, a good point to kick off the final story arc. As for what exactly she'll do, my bet is on her launching a new...age of magic, or perhaps age of heroes, much like in Shadowrun. It's also conceivable that this is not the first time this has happened--perhaps All Myths Are True, and Zeus, Odin, etc. were beings just like Haruhi.

Haruhi is the true Nietzschean Ubermensch
Think about it. She rejects the norms of society, doesn't give in to the majority's pressure, lives by her own "code" and standards, and wants to make a better world (well, better by her definition). And she even has followers of a sort who are compelled to follow her.
 * The Other Wiki actually had this sometime before under the article for Haruhi. It has been deleted since.

Haruhi is everyone.
Her powers had been passed down to her, and (as far as this troper knows) it hasn't been revealed from who or what Sasaki got her powers. It's possible that the "god"s typically undo any knowledge their predecessors had of the reality warping power, and/or any damage done. Every time a Haruhi-power wishes away the power, or successfully "makes a new universe" that pleases them (but without being able to create or destroy life, only alter what is already there), it passes to the next person, somewhere near the same time and astronomoical coordinates as their predecessor. Eventually, it will loop around to the "first" being (or at least loop, there wouldn;t really be any first, it being a Stable Everything Loop), after everyone else to have the power slowly made the universe exactly what it was before the "first" person changed anything.

The Unwanted Harem was set up by Haruhi so that she could win.
Her obsession with winning is rampant during the series, and given how Genre Savvy she is, it makes sense she would expect one of these to come up. This means that the real reason she almost destroys everything in Episode 6/14 was not just because she saw Kyon friendly with another woman, but because Mikuru was winning. The kiss made her believe she was back on top, so she restored everything. Also, notice how every other member of the harem has a ridiculous number of reasons to not be with him (it's forbidden, not human, male, it would mean everyone dies, etc.}. This is Haruhi subconsciously getting Kyon to notice her and only her.
 * Plus, she's the first girl introduced in the series. But the again, there's Sasaki and Kyon technically met her before the series started. Although, Kyon did go back in time three years to meet a younger Haruhi which happened, chronologically, first... Gah, I'm so confused!
 * It's possible that her subconscious recognises that she met Kyon three years ago, but hasn't realised that the Kyon from that point is from the 'future' (because Haruhi doesn't really believe in time travel), so she still thinks she was the first. Alternatively, she just didn't know about Sasaki, and so never did anything about her.

Like the big blue glowy things, Haruhi's groping of Mikuru is a way of getting off a different kind of stress.
If she doesn't touch Mikuru's breasts, the world will end.

The "Haruhi" Universe is really a dimension made up of Haruhi's beliefs, but she actually is physically in another dimension, where her body is in coma
Therefor, the series ends, if she either dies in her true dimension, or if the others find a way to send her back to her real life, which would mean farewell. She would probably end up searching everywhere for a brown-haird boy she can order around... Oh, yes, that would explain why her parents are never shown, but mentioned. Her parents are still in The Real World.
 * This raises disturbing questions on what happens to the Dream when she wakes up.
 * Alternatively, Kyon is the sleeper. Evidence pointing towards this, during the Magazine arc, each of the Nakama came up with their own stories. Mikuru wrote a conglomeration of fairy tales that ended on the note that when "Prince Charming wakes up, everything changes."
 * We do see Kyon waking up an awful lot.
 * And grumpily, at that. Clearly, his subconcious knows that he's not ready to wake up for real.
 * Or, this troper's preference, Haruhi (or Kyon) is having a dream each night that corresponds to roughly one episode. The two-part vacation episode with the typhoon was when he or she had am\n extra-long fever dream from being out in the rain. The character just never remembers their waking life inside the dream, and if it's Haruhi, she just doesn;t notice anything because then it would ruin the rest of the dream for her.

Everything is a Gambit Roulette / Memory Gambit by Haruhi.
Haruhi purposely set up things in a way that would lead to the speculations done my Yuki, Mikuru, and Itsuki, and planned that she would lose her knowlege of her being a Reality Warper later and planned that the members of the SOS Brigade would come to keep her under control for these reasons to prevent the apocalypse. For some unrevealed reason. She's been influenced by Light "God of the new world" Yagami.

Haruhi, or some other cast member is a contributor to the wiki, and a shameless Entry Pimp
Which explains the amount of examples and WMG's. While Haruhi might just be that narcissistic, my money's on Mikuru who really doesn't mind her advances that much, seeing she is nostalgic in her future form.

Haruhi is a Composer
Think about it. Haruhi's closed spaced where giant beings rampage is the same as Joshua's Shibuya Underground where beings known as the noise rampage. The instant Haruhi discovers her almighty composer powers, she'll come to the same conclusion that Joshua did and cue another instance of the reaper's game.
 * Alternatively, she's already playing a Reaper's game with her Conductor and her entry fee was her memories of the Underground.
 * Or the Reaper's Game is what the SOS Brigade is to Haruhi. All the problems in the game started when Joshua got bored.
 * The problems in the game started because Joshua decided Shibuya needed to be destroyed before it had a chance to corrupt the other areas.
 * Maybe he thought boredom was catching? Anyway, nothing like a bet to make a God-like entity happy.
 * Tsuruya is Haruhi's Producer.
 * But who's the conductor?
 * Uhh... Kyon? (Maybe they had both agreed for a game, just like Josh and Kitaniji with the entry-fees beeing their memories?)
 * So how does Sasaki fit into this?
 * She was the previous conductor, and Haruhi got her powers from defeating her.
 * Kyon's sister is actually the current GM and is also acting as the Conductor due to Kyon's entry fee making him unable to perform his duties.
 * Kunikida is a Support Reaper.
 * Alternatively, Haruhi is the Composer-queen, who rules over all planes and even the angles are afraid of, because she has so much power!... And Joshua's cousin. I always thought those two were at least related. Their personalities are sometimes SOOO simmilar: People are dull and boring? Erase them. People are evil? KILL them with magic powers! Life is unintersting? Pep it up with your magic powers!
 * Since the Undergrounds are different by preference of the Composer, the Osaka Underground game is played over a far longer period of time. If Haruhi is the Composer, Kyon is the Conductor and Tsuruya is the Producer. The pairs who are playing the game are: Yuki and Ryoko, Koizumi and Mikuru, Taniguchi and Kunikida, Emiri and the Computer Club President, Arakawa and Mori, Sasaki Kyouko, and Fujiwara and Kuyo. When Asakura was Erased, Tsuruya gathered her soul and made a noise from the remains in the form of Achakura from Haruhi-chan.

Haruhi doesn't currently have her reality warping powers
Despite no longer having her reality warping power Sasaki retains the ability to create enclosed spaces and could presumably generate avatars if she desired to change the world. In order for Haruhi to make a large scale change her enclosed space must grow to a certain size. The rampaging of Haruhi's avatars are what causes her enclosed spaces to grow. As of the latest novel Haruhi is generating avatars that aren't rampaging.

Haruhi's powers do not manifest her own subconscious whims, but the notions of anyone else
This is a belief I came up with because, well, it is the ONLY way I can look at Haruhi and the entire show with some kind of basic acceptance. In reality, Haruhi is nothing more than a sad, scared girl, aware of the true nature of her powers but unable to do anything about it. It comes down to a situation similar to Your Mind Makes It Real. If someone aware of Haruhi's alleged "nature" thinks she's angry and going to destroy the world, it will happen. If someone thinks she's bored and the Universe will alter itself to be more amusing for her, it will happen. This explains why the world hasn't ended or gone under rampant rewrites during the course of time Haruhi is out of the eyesight of the SOS brigade.
 * If this were the case, why wouldn't she speak up? She could just tell everyone who thinks she's about to destroy the world that she knows what's going on and isn't going to do that.
 * For one, political reasons. Mikuru, Yuki, and Itsuki's superiors do not see eye to eye, but I may be mistaken. By carrying on as she is, Haruhi is presenting an Enemy Mine scenario and keeping the three factions more or less united. She may also may not wish to come out with the truth because it would be * VERY* easy for someone to abuse this power for their own end.

Haruhi's power is actually a manifestation of Spiral Power
Or possibly its the other way around. This is based mainly on Yuki's explanation for why the Data Entity is interested in Haruhi, namely the autonomous evolution thing. In addition to this, it seems to me that Haruhi's determination, refusal to take no for an answer, hopefulness, and just personality is usually very similar to what's needed to access large amounts of Spiral Power.
 * Is Sasaki an Anti-Spiral, then? She doesn't try to prevent other people from using Spiral power, but she doesn't know it's dangerous. Her team, however, DOES want it for her, so maybe they are also Anti-spirals

Haruhi created the Sky Canopy Domain, evil...ish espers and time travelers when remaking the world at the end of the first novel/season.
She didn't start creating a new world just because Kyon was upsetting her by flirting with Mikuru. She was bored with the world because as far as she could see, the aliens and whatnot weren't coming or weren't there at all. So she made versions that would come to her and actually do stuff. The result? A new group that is more hostile/weirder and is focused on her and without as strong an inclination to keep her out of the loop. Now she can be entertained! Except by this point that's not what she really wants anymore. Uh oh.
 * So, Sasaki is a part of her personality that just doesn't care about anything (although she never did care too much)?
 * Yep, Sasaki is The Melancholy of Haruhi Suzumiya.

Haruhi is the source of her own power.
Eventually Haruhi is going to catch on. With the cat out of the bag, someone will decide to ask Haruhi if she has any clue how the hell she got her powers in the first place. Haruhi will then make up her own bizarre and nonsensical origin story that thanks to her reality warping powers will retroactively become true thus giving her her reality warping powers.

Haruhi knows exactly what's going on, is in better control of her power than anyone thinks, and playing along for shits and giggles.
There's nothing more messed up than thinking about a God that's duping everyone and getting away with ridiculously questionable acts and having complete freedom, since nobody would try to oppose her. Trying to end the world when Kyon talked to another girl? That's just her messing with everyone and denying Kyon even a single facet of a normal life. Molesting Mikiru is just an act of a Depraved Bisexual and she loves the fact she gets away with it. All the bad things that have happened in the series? All Haruhi wanting a little more "excitement" in her life, regardless of who she has to step on along the way. Nightmare Fuel if ever there was one.
 * Actually that kinda has Fortunate Implications. It means that her morality is improving due to "lesser" beings later on in the books.
 * Unless she just wants them to think that way.

In the past, Haruhi attempted suicide.
After her realisation that she was totally insignificant in the grand scale of things, Haruhi went into a deep depression. It culminated in an attempt at suicide, which failed for... some reason. (Interrupted?) After some councelling, her view of the world changed into her current one (Find the interesting instead of just waiting for it).
 * Here's how it went down: in an attempt to keep Haruhi from destroying the world, one of the antagonists (could be old or new) of the series travels back in time as far as they can (three years). The antagonist then manipulates events so that within a very short time period, three-years younger Haruhi has decided that her life is completely meaningless and attempts suicide. The present brigade learns of this plot and goes back in time three years, where they foil Haruhi's suicide, and through the Power of Love and the Power of Friendship, convince Haruhi that life is worth living because there are always new things for her to discover and learn about. With the plan foiled, the antagonist has a fit and tries to kill the three-years ago Haruhi. The brigade protect her, and the ensuing battle reaches epic proportions as all factions in the story jump into the fight. During the confusion and chaos, a mistake is made by Yuki's superiors, wherein a glitch occurs and Haruhi is given god-like, reality warping powers. An epic beat down occurs as Haruhi destroys all of the antagonists. The glitch that resulted in Haruhi's power-up cannot be fixed, but Yuki's superior's are able to wipe Haruhi's memories of the events. The brigade returns to the present time line, and thus both the series backstory and climax are accomplised in one go.

Haruhi is aware that her powers need to be kept under control and gathered everyone who observes her for this reason.
Think about it, if Itsuki and the rest of the organization just one day realized about their powers and Haruhi, then maybe Haruhi intentionally created them so there will be some to take care of Sealed Realities and prevent her from destroying the world. Why? Because she always knew that she is God, but also feared Laser-Guided Amnesia because she knew there was the possibility that she might forget. How? No idea. But three years ago, Haruhi indeed forgot, and prepared The Plan- the moment she will forget, there will be someone created to keep her under control.

If Haruhi realizes her powers, she'll become an Energy Being
The only thing that keeps her human right now is her belief that she's just a normal human. If she ever realizes her powers, she'll become an ABSOLUTLEY omnipotent being, that cannot be grasped, unless she wants it. Her powers wouldn't than be subconsciously anymore: If she only thought about, for example, Santa Claus falling onto Kyon's head, it would happen.

If Haruhi knows about her powers and consequences, she'll give up them.
She'll conclude that she never really needed them, and what she always needed were true friends. And this will open a breach for the true Big Bad, that will destroy the Universe. Her Closed Spaces, and to some extent, the very existence of her powers were actually keeping it at bay.

Haruhi beleives that "John Smith" is living the life she wants.
When Haruhi asks "John Smith" questions, his answer to the question on is "I haven't met them yet". It was only later that Haruhi relised that if he said "I haven't met them yet" probably meant he has met something amazing and possibly lives an extrordinary life. Thus she only to fail. Not giving up she enrolls into the school to find clues that only a student could find, such as past members of clubs.
 * You know, that actually makes a lot of sense. I agree, and adding to that, all yuki had to change the world in Disappearance was make Haruhi Believe he was lying, thus changing history.

Haruhi is in love with "John Smith."
Related to above she sees him as living this incredible, exciting, romantic life that she wants to be a part of with him. Her initial interest in Kyon is because he reminds her of him (the two being one in the same) but later has trouble reconciling her attraction to him with that of her "true" love. Notice that when the alternate Haruhi in Disappearance finally meets "John Smith" for the first time in three years she is much more friendly and accommodating of his behavior and ideas than the regular Haruhi is of Kyon's.

Haruhi really is God.
She's projecting her powers onto Kyon, but he doesn't want them and is projecting them back.

.... Just a thought....

Haruhi isn't God.
Nobody shown in the series is. She happens to have reality-altering powers, but the reconstruction was taken out of pity by the true God, that has yet to appear as a character in the series.
 * This is supported by the new opening which contains the statement "Gott ist tot" (meaning God is dead), and thus no living character is God.

Haruhi heard a rumor about Kyon's meeting with Yuki after school, and it was a contributing factor to her remaking the world
It is commonly agreed on that she was jealous of Mikuru's flirting with Kyon. However, she does not call Mikuru out on this, and she simply broods on it. If Tanguchi spilled the beans, or if she got wind of the meeting some other way (For example, if it was a Plan by Asakura) then she would feel like everybody had a better relationship with Kyon then she did. Of course, Koizumi talks to Kyon more than anyone else, so she figured that she wasn't as liked by Kyon as everyone else. Since she was the one who brought all of them into Kyon's life, she wanted to take them out and start all over. The kiss and compliment during her dream made her realize that Kyon DOES care about her as much or more than he does the rest of the brigade.

Mikuru, Nagato, Itsuki, Tsuruya, Shamisen or whoever you Kyon can be shipped with all do have feelings for him... because Haruhi does.

 * Assuming Haruhi does like him, which is pretty much the only confirmed attraction in the series, that means she would rate him highly. If she believes that Kyon is actually highly attractive, wouldn't that automatically make him so? It's not a matter of looks or even necessarily being his personality; if she likes him she would likely believe that everyone else that liked guys would also like Kyon. So they do.
 * Well, this is might be partially true. In book 4 when Haruhi was taken out of the equation, Mikuru, Tsuruya and Itsuki all seemed less attracted to him. However, Yuki was more overtly attracted to him.
 * Hm. Since Nagato rewrote the world while presumably being attracted to him and also making herself more expressive, it makes sense that how she felt would carry over. Also, unlike Haruhi, she would actually be aware of what she was doing and maybe went out of her way to make sure there wasn't any spillover, so to speak.

Haruhi erased her own memory of being a God or whatever she is
If anyone became omnipotent, I would suspect they would become extremely lonely. Everyone would be pleading them for something, praising them, or whatever and noone would treat them like an equal. Haruhi became distressed at this and had no friends, only worshippers Haruhiists. She then began disguising herself as human, but once she did this, it was no good because she either had to not help people when it was in her power to do so or blow her cover. Therefore, the only thing one can do in this situation is to wipe the memory of your powers from her mind and have them activate whenever they need to to keep her happy. Given the way loli-Haruhi wrote "I am here" it was this being merging with Haruhi and wiping its own memory. If it used to reside in Sasaki, then it was attracted to Kyon due to Sasaki, and jumped into Haruhi to have a better chance with him, for whatever reason.

This could also mean that when Yuki took Haruhi's power, she was actually rerouting the being into her own consciousness. It's also possible the being thought it had a better chance as Yuki than as Haruhi.

Haruhi lied about what she had wished for three years ago.
She didn't wish to become a very interesting person on the planet. She wished to meet the most interesting on planet, and be a part of his interesting life, and to be told that she wa sspecial and unique. And thus Kyon was created. Of course when she did not immediately meet Kyon she decided on the enxt best thing and become that person herself.

When Haruhi ovulates, the universe changes in very interesting ways.
Of course, we don't hear about those stories because then they wouldn't appeal to as big a demographic. But boy, if you thought laser beams coming out of someone's eyes was impressive...

Haruhi really is Jesus. In Purgatory.
S/he's working off the sins of the human race, but like Neo in The Matrix, is able to warp the spiritual world around hir. Kyon is a mindwiped, and  , it was to keep his world intact instead of Haruhi having to go to Earth and start the Rapture.

The entire SOS Brigade is Jesus
Both were created by God/Haruhi and tries to take the sufferings imposed by God to themselves in order to save us.

The reason why Haruhi's bahviour is so messed up is, that she doesn't know what she wants herself.
Haruhi is searching for something special anywhere, because she feels the desire for... something. But she can't determine what that something is, so she just decided it has to be supernatural. In reality, however, this "something" is just having friends and being truely appreaciated by those friends. Enter SOS-brigade.

Haruhi really IS the director of the show!
Think about it.

Haruhi is real
Our world only exists because at some point after the show she thought "wouldn't it be cool if my life was made into an anime?", so our world was created for her world to be an anime in.
 * My iPod on shuffle for its 975 songs played "Lost My Music" exactly when I was reading the ENOZ concert part in the novel. I only have 1 copy of that song.
 * That might be a bit of a stretch, but it's possible that the anime was created in our world because Haruhi wished for it in her world.

The entity known to fans as O-Haruhi-Sama is a separate entity from that of Suzumiya Haruhi.
When the Integrated Data Entity first noticed Haruhi, it was because of a sudden, nearly impossible increase of data focused on her. This may be because of the entity, similar to the Integrated Data Entity but on a higher order of life, moving to inhabit her, while granting her wishes in a subtle way while just as subtly guiding her to a path that would result in it reconnecting with Kyon. It has found some form of infatuation with Kyon. As Yuki Nagato stated the Integrated Data Entities are an evolutionary dead end, unable to change like organic beings, of which only humans have gained sentience as well as self-awareness. It is the reason that humans developed sentience despite being organic creatures. The data transfer to Haruhi casued what appeared to be, to it, some slight interference, but to the time travellers and Integrated Data Entity caused an impassable rift in the time continuum and an impossibly large torrent of data, respectively.

Haruhi has a male counterpart
Why is she a girl? God has been depicted as male for the majority of history. Personally I think He/She/It/God would prefer to not chose a gender because He/She/It doesn't want us to view one or the other as superior. The solution? God split itself into two individuals, one Haruhi, is the female aspect of God. The other, (Perhaps Kyon, perhaps someone unintroduced as yet) is the male aspect of God. Following this logic the two should have opposite viewpoints and personalities, yet still get along together pretty well. (Note that this troper hasn't read the novels and so cannot explain how Sasaki fits into this.)

The existence of aliens, time travelers, espers, and the series in general is all because of The Adventures of Mikuru Asahina.
Okay, lemme put it this way: in Timeline A, Mikuru, Itsuki, and Yuki were all normal people in the SOS brigade. Haruhi is still a reality warper. In this timeline, nothing of nominal importance has happened, so Haruhi decided to make a movie out of boredom. She puts an alien, a time-traveler, and an esper into her movie because she wants to find them and is frustrated. That, combined with her reality-warping, made Yuki, Mikuru, and Itsuki how they all are, and created the IDE, Mikuru's orginization, Itsuki's orginazation, and a new timeline in a sort of Cosmic Retcon. This new timeline, Timeline B (the "true" timeline) is formed from that from a common jumping-off point (the "John Smith" thing), and the rest, as they say, is history.
 * Not really: the casting decisions were based on Kyon's "Revelation" to Haruhi at the end of Melancholy. She just took his words for inspiration for the roles. So, jossed, in other words.

Haruhi's initial character was strongly inspired by Pippi Longstocking
The similarities: eccentricities, odd hair, abnormal strength, etc. It's all there. In fact, one would venture to say that the similarities are too close to call coincidental.

The SOS Brigade was assembled as Haruhi (or Kyon's) own personal harem
Of course if it's Kyon, he needs to have a long talk with his subconscious about Itsuki.

Reality in the Haruhi-verse is a computer/the internet...
Haruhi is the CPU or the OS, Itsuki and Mikuru are different types of anti-malware, the Integrated Data (Thought/Sentient) Entity is/are the user(s) with the human interfaces as their GUI, and Kyon is the Power Source. I mean, there does seem to be a computer motif occasionally, especially with Yuki.
 * If we want to make a * nix analogy, Haruhi is init, Yuki is bash (Or some other shell or desktop environment. Most likely the different interfaces are... different interfaces. Perhaps Asakura is Gnome or KDE, since she appears to have a more apparent personality?), Itsuki is clamav or somesuch, Mikiru (I don't think we've seen any other time travelers... just Mikiru and Mikiru) is kjournald, and Kyon is just an ordinary program (hence Itsuki's "background check" reporting "perfectly normal", that is, neither malicious nor a crucial system component)... that happens to be running with suffecient priveleges to run telinit.
 * In fact, it seems Nagato's powers only functioning "for emergencies" is because Nagato isn't always running as root, because that would be stupid. Of course, sometimes one really does need to su and do something (for instance, locking out a hacker's access and killing their shell). The event of Nagato getting fed up and making Haruhi appear to not exist may be what happens when bash-tan runs telinit 1 out of anger... init no longer is personified, but instead exists as the Emergency Escape Program. Perhaps the spinoff shows are the result of Kyon deciding to telinit 3/4/5/whathaveyou for a change of pace.

Haruhi knows it's a series.
She lets Kyon and the SOS Brigade keep up The Masquerade because breaking it would mean a Snap Back (such as Laser-Guided Amnesia, which would be annoying to fake and unacceptable to enact on herself) or the Series Finale (fixable only by Plot Leveling, which would mean Haruhi wouldn't be the most powerful being in the universe any more). The reason she sometimes shows guilt or oddly-directed worry over certain things that go beyond what she expects (like when she painted herself into a corner by  in Remote Island Syndrome) is that she actually knows what she's doing, and worries if it might be endangering others.

Haruhi's powers come from sheer stubbornness.
"Haruhi believes her values and judgment to be absolute. She does not understand what others think, or realize that they may think differently, or rather, it has never occurred to her that her way of thinking may be completely different from othersâ€™ since the beginning. If people want to achieve time travel, just put Haruhi on a spaceship. Since she probably wouldn't give a damn about the Theory of Relativity anyway." ~ Kyon

This means Haruhi is so stubborn and self-centered that even the laws of physics know better than to argue with her.

The Plan to keep Haruhi from realizing the truth is suicide for everyone.
So Haruhi, a God who is maintaining reality itself, believes herself to be a normal girl. She lives a normal, if eccentric life, with shadowy friends keeping everything that might convince her otherwise out of the way. She grows older because she thinks she should. Around age 110 or so, she thinks about how people that usually die. So because she's expecting it, she dies. Her perception becomes a completely blank slate; and ALL OF REALITY follows suit.
 * Or, at least, she will destroy the world and replace it with an afterlife.

Haruhi's desire to create the ultimate Moe character is what resulted in Yuki gaining emotions.
So she has created the ultimate Moe character. Once more, she doesn't see what's right in front of her.

Haruhi will become a writer in future
Just after Kyon and the rest of SOS Brigade will realize it's the best way to keep her bot entertained and busy enough to not alert reality, they will slowy set her interests toward creating some kind of works of fiction. Haruhi will becaome writer (ro movie director, or something like that) and create things that for some reason weren't created in her world, even though they exist in our. Nobody will be aware that while Haruhi would acknowledge what she creates as only fictional, her subconscious wish will make all worlds exists as an alternate dimensions. Her works will of curse all have strong infulence of Rule of Cool and/or Rule of Funny and be very Troperiffic. The most popular of her books will be:

- Cycle about sucessive generations of family with unusual powers, fighting vampires, nazists and other stange beigns.

- Adventures of teenage wizard girl and her friends who lives in crazy fantasy world and do unbelivable things.

- tale about young boy and his friend who are breaking laws of physic with the help of giant robots.

If Sasaki would do the same, she will create most of worlds mentioned in Crapsack World and Wangst tropes.

Haruhi might become a dictator in the future
She is practicing it right now through the SOS Brigade.

This is all a convoluted plan to get Haruhi the most interesting boyfriend ever.
Near the beginning Haruhi admits that she'd date anyone as long as they were interesting. She seems to like Kyon, but (according to Itsuki) he's completely normal. Considering she was hoping for a time traveler, Esper, alien, or slider this is quite depressing. To fix this she's been rewriting the world so that instead of being normal Kyon becomes all these things. Kyon times back in time during Bamboo Leaf Rhapsody. If you define Esper as person who enters Closed Space and stops the Celestials then techically he's an Esper because of the kiss. I haven't gotten far enough in the books yet, but you might be able to count his existence in a changed world as an alien or slider.

Haruhi chose Kyon as her stand-in to discover supernatural things
She desperately wants to meet Aliens, Espers, Sliders, and Time Travelers, but her common sense won't let her accept their existence. So what does she do? She chose Kyon, who as a youth once shared her passion for the supernatural, to discover them and have adventures as her proxy. This is also why he comes to enjoy his exciting and abnormal life.

Haruhi is a self insert of Strong Sad (from homestarrunner.com)
Itâ€™s even crazier than you think. If you think about it, having a normal (in H Râ€™s crazy canon terms) could be the cause of Strong Sadâ€™s depression, and Haruhiâ€™s depression (slight one) was also the cause of having a normal life. So one day, he created the Haruhi universe, with Haruhi herself as his male counterpart. Donâ€™t ask for a clearer connection, it makes much more sense when you think less of it.

In Haruhi's world, Everybody Is Jesus in Purgatory
Everybody is suffering from having to take care of Haruhi just to please her, but it is all because of everybody atoning for their sins.

Haruhi is not The Messiah version of Jesus.
A true Messiah is a person who puts other's needs and troubles before himself/herself (referenced the Original Messiah, Jesus) Even a Dark Messiah puts his beliefs before his needs, even though it is done in a Well-Intentioned Extremist way. Jesus, for example, served humanity and died for its sins. Haruhi, on the other hand, makes slaves of her disciples instead of teaching them how to reach Nirvana. She doesn't even look like Kamina, the closest analogue to Jesus (Kamina did serve Simon, but Haruhi has more servants). Instead, she is the closest analogue to the easily-bored Old Testament God. She might be Jesus in Purgatory, but she definitely isn't the messiah.

Haruhi is the Collective Unconscious
Her "easily-bored" personality and her ability to destroy everything when bored is the representation of humanity which does everything from memes to war because they were bored.

The real reason why Haruhi's powers are so dangerous is because of her teenage years
Adolescence is usually considered the most unstable part of a person's life (aka the title, The Melancholy of Haruhi Suzumiya), so if Haruhi grows up, her powers will stabilize, and there will be no need for observers.

Haruhi, not God, will pass judgement on the world
She will see if the world will still be a suitable place to live in. If the world is boring, it will be annihilated.

Haruhi's powers (and Kyon's nickname) are results from fragments of the Skasis Paradigm being stuck in her head.
(Note: This entry is based on second hand knowledge of Suzumiya Haruhi.) Remember the events of "School Reuinion"? Chances are, the Krillatines did not just focus their operations in England; logically they have operations in Japan (most advanced in electronics) as well. The Tenth Doctor only managed to foil the Kirllatines from unlocking the 'central command unit'; other fragments of the Skasis Paradigm, granting various 'powers', were still decoded succesfully-albeit not in control by the Krillatines but by the decoders (i.e. the children) themselves. Two of the 'genius children' the Krillatines were using happened to be Haruhi and Kyon. Thus, without the 'central command unit' being used by the Krillatines, those two were free to run around with partial power of the Skasis Paradigm stuck in their heads. Whereupon Haruhi decided to use it to create a new, alternate universe completely (3 years ago, to be exact) and Kyon, from the Skasis Paradigm, decided that "John Smith" was a pretty nice name (and, if the 'slider' theories are true, he also has the 'transdimension travel program' stuck in his brain too).
 * This has nothing really to do with this, but this troper just noticed that Skasis is almost an anagram of Sasaki.

It's all HARUHI'S dream.
Haruhi is a teenage girl, and as we all know, teenage girls are brats who want the world wrapped around their fingers. At the same time, Haruhi wants to be special and hang out with special people, so she's dreaming of a world where she controls everything, gets a hot love interest, gets to act as bratty as she wants since anyone who denies her will bring about The End of the World as We Know It, and hangs around with people that have amazing powers. The dream is actually several dreams combined, however, since Haruhi just isn't satisfied with the fact she isn't getting what she wants directly and keeps trying and trying to get it right. It's more of a daydream that way.

When Haruhi FINALLY discovers her power, she'll become Drunk on the Dark Side.
The SOS Brigade will have to destroy her when she becomes a danger to the universe as a whole, and Kyon will be the only one who can. After he succeeds, Mikuru and Yuki somehow reset time and space so that it would seem like Haruhi never existed. They also reset Kyon's memories so that he never knew of Haruhi or them. They all return to their respective lives, and a Bittersweet Ending is had.

The ponytail was a test.
Haruhi never wore a ponytail after that day. The ponytail was a test to see if the dream was real. Haruhi knows that it was, now.
 * The test failed because Kyon didn't say something like: "Hey, I said a full ponytail. You were supposed to grow it out overnight. Now get it right next time."

Haruhi doesn't really have the hots for Kyon.
Haruhi doesn't want to be in a world where Kyon is kissing her (which is why she stopped remaking the world), she either wants Mikuru or distrusts her (hence the jealousy). After all, Haruhi isn't really one to hide her emotions. If she did have the hots for Kyon, she wouldn't hide it with bullying him. Which means that she was right all along: She wants someone weird. Then again, Haruhi does like being proved wrong.
 * Or she could have thought that having a guy she likes kiss her means "This can't happen; it's totally a dream" and fixes reality. That kind of thing tends to happen.

Haruhi is an ordinary human.
Tanigawa Nagaru is a New Agist, and a believer in Human Potential. Haruhi is able to tap into the powers that all ordinary humans have.
 * So it's like Akira?

Haruhi doesn't mean THAT kind of slider.
Nobody ever asked what kind of SLIder she meant.
 * Haruhi wants one of those little hamburgers sold in America (Then again, she does kind of have a thing about baseball).
 * So basically Haruhi and Kyon Go To White Castle? Holy crap. Even their name fits.

Haruhi is the only REAL human
Everyone is an interface of the Data Entity which somehow failed.

Haruhi is a Kyon/Yuki shipper.
At the beginning of Snow Mountain Syndrome, Koizumi claims that the incidents of closed space have gone down since Christmas, around the time when, it is later revealed, Haruhi thought that something was going on between Kyon and Yuki. She also flips out at Kyon's perceived indifference to Additionally, in Charmed At First Sight LOVER, when Haruhi finds what she thinks is Kyon's love letter to Yuki, she's less bothered by the thought that he'd write one than she is by the sheer absurdity of the letter itself. To be fair, though, it is rather cheesy.
 * Which makes sense that Haruhi didn't want to be in the 'closed space' with kyon after he kissed her, she wanted him to be with Yuki not with her.
 * Except what Koizumi said was that 'Closed Space has become less frequent, as I told you at Christmas.' Not 'Since Christmas, Closed Space has become less frequent.' Haruhi being more pissed at the cheesiness of the letter than the confession it contained is... unlikely.

Haruhi's attempted sexual assault on Mikuru was a jealous attempt to be Kyon's First Kiss.
Unless Haruhi is just messing with everyone, she still thinks episode six was All Just a Dream. As far as she knows neither she nor Kyon has kissed anyone. While filming the movie Mikuru offers Kyon her water bottle. Haruhi grabs the bottle knowing what it would mean if Kyon drank from it. Shortly afterwards, the movie calls for Itsuki to kiss a passed out Mikuru. Since there was no way to force the chore boy to kiss the director, Haruhi wrote in a less violent version of Murder the Hypotenuse to make herself more desirable.

Haruhi created the Anti-SOS-brigade on purpose, in order to give her "Team" antagonists.
Due to Kyon spilling the beans to her (even if she apparently didn't believe it), Haruhi is to some degree aware of what is happening around her, but afraid it could become too boring and everyday, if the conflicts start to become resolved. She therefor created the Anti-S.O.S-Brigade and Retconned them into Canon, in order to keep the story interesting.
 * Well, probably Haruhi created the WHOLE WORLD, so obviously EVERYTHING in it is caused by her to some extent.

Haruhi employs Obfuscating Stupidity
She is well aware of her powers, and she is just testing us. Or does she?
 * It could even be that she is just doing this for her own amusement. She is well aware of the trouble she causes, and she finds the sight of everybody scrambling about to be highly entertaining. She keeps adding extra complications, like the Canopy Dominion, to stir things up. It even looks like Mikuru is most on top of this and simply does everything in her might to keep Haruhi from being bored--up to and including offering herself.

The universe is Haruhi's Never-ending Story
For those who don't know the Never-ending Story, it's about a world of fantasy being brought back to life by a young kid through means of a magical book. Believing in that world gives Fantasia existence. As the kid transports into Fantasia using the magical book (The Neverending Story, and he keeps wishing and imagining, he starts forgetting something about himself. So what would happen if a child like Haruhi got hold of that magic book? Why does time travel can't go back to three years ago? Simple, because the world the protagonists live in IS Fantasia. Haruhi's common sense dictactes that there is no magic, but instead, it has time travelers, aliens, espers and sliders. It was all created by Haruhi. So, she ends up being, by all intents and purposes, God. Maybe this would also explain why Nagato became a bookworm. She's searching for that very same book.
 * The reason the kid loses his memories is because they are exchanged for having his wishes granted. Furthermore, he doesn't have to explicitly make a wish for it to be granted. Thus, Haruhi created the Espers to act as a restriction on her powers so she wouldn't over use them. Also, the kid's powers are granted by a magic item given to him by the Childlike Empress, who is for all intents and purposes the actual God of Fantasia. Given that the Anti-SOS brigade believes they need Kyon's consent to take Haruhi's powers from her, and that the Childlike Empress will only meet a given person once in a lifetime (and thus can not be Kyon), Kyon is clearly the anthromorphic personification of said magic item. Also, The Neverending Story is explictly not one of a kind so Yuki wouldn't need to find the exact same book Haruhi used.

God has died in the Haruhiverse. Literally
And he gave his remaining powers to two people, Haruhi and Kyon.

Hera and Zeus are Haruhi's actual parents.
Haruhi Suzumiya. Looks like a child of Hera and Zeus corrupted with Engrish and disguised as a Japanese schoolgirl.

Haruhi's powers are due to not Kyon being God himself, but because she is the collective unconscious that is projected by the "normal" human race, Kyon included.
This is a theory that would be only plausible if Kyon really is God. Some people from the fandom are trying to convince Kyon is the one who is projecting his own powers to Haruhi, giving Haruhi seemingly godlike powers despite not being its owner. However, Kyon constantly tries to convince us that he is nothing but normal. Of course, this either means on a literal scale, Kyon is unaware of his powers, or on a metaphorical scale, Kyon is the representative of the normal people who are trying to convince themselves into not having powers, and because those powers have to go somewhere, it went into Haruhi. How is she the unconscious, then? Normal humans are trying to hide their powers into their unconscious, which then accumulates and grows up in the collective unconscious, in other words, they refuse to be conscious of said powers. With all the gates closed, the powers flow to the remaining windows: weird people. In reality, humans have the ability to change the world, but they are constantly trying to suppress it through their instinctive denial of something that powerful in order to be "normal", so the remaining powers often end up to those people who accept weirdness.
 * Probably some of those people who accept weirdness are in TV Tropes... Oh my, TV Tropes is Haruhi!

Haruhi has a potential to be a Magnificent Bastard, the reason why she doesn't show that potential is because she requires a Death Note
It would take some time before Haruhi takes a joke called "Death Note" as fact, and then Change The World......

When Haruhi uses TV Tropes, the world changes into seemingly bizarre ways.
Too bad we often forget.....

Haruhi will find out about her powers.
There will be some crisis, or Kyon will finally get fed up, and tell Haruhi about herself. All hell breaks loose, And everything is solved at the end with a mindwipe.

Haruhi's energy stare in Day of Sagittarius actually worked...
...it was just delayed a bit. Kyon may have said he felt nothing but mortal danger, but as soon as the fighting started, he was yelling orders at his computer screen with all the energy and confidence he had asked Haruhi for. Itsuki even remarked on the change. "Itsuki: It sounds like someone's getting into this game."

Besides, can you think of any other way Haruhi's order to "launch the Gunda(beep)s" would get Kyon to reply with actual enthusiasm?

Haruhi is an Antichrist in the Good Omens universe.
Both Haruhi and Adam have reality warping powers that can cause the Endofthe World As We Know It. Haruhi is being watched by other organizations that don't want the world to end.
 * Madoka out of pure selflessness and a desire to help others. Haruhi is almost completely selfish. Hence she is the Antichrist to Madoka's Jesus. Of course, since most anime universes are CrapsackWorlds, the opposite could also be true...

"Them" and the "SOS Brigade" also have similar transitional natures.
 * There are also angls and demons watching her. They may or may not be somehow related to the Data Entity.

Honestly, it gets better. (I can't believe this idea is already on this page. I've been thinking of it for a while.) What was one of the main identifying signs of the Anti-Christ? A Hellhound would come at the start of the year of the end of world. Its form would be determined by the Anti-Christ's wants and personality, and would function as a servant, protector, and herald. Now, whose name (according to the Meaningful Name entry on the main page) translates to "Dog" in Ancient Greek? If you said, Kyon, you get the prize. Also, the members of the SOS Brigade map rather well to the Four Horsemen of the Apocalypse:
 * Yuki = Death
 * Mikuru = War
 * Itsuki = Pollution
 * And I guess either the Slider or Tsuruya can be Famine.

Now, someone please write this crossover?

When she recreated the universe 3YA, she learned just about anything, abet subconsciously.
This requires a few assuptions, so bear with me here. During Bamboo Leaf Rhapsody, Haruhi asked about Aliens, Espers, Time Travelers, and Sliders. Note that the first three are known to exist in the universe. She didn't ask about wizards or robots, which we don't know about. If we assume that Haruhi remade the world Three Years Ago, them you can assume it involved bringing the data from the old universe and putting it into the new one (which started as Closed Space). All that data went through her, so she vaguely remembered the fact that ATT&E exist, and she was just looking for confirmation. Also note that she is The Ace at just about anything she tries and gets good grades without even trying. Even when she has been known to sleep in class, in the rather competitive Japanese school system.

Haruhi wasn't listening at all during introductions.
Haruhi (her personality at that point in time) strikes me as the type who was either listening really closely for anyone weird, or was just waiting for her turn to introduce herself. It supports the theory that Kyon's real name is John Smith.

At some point before Haruhi rewrote reality, the anime was live action.
Haruhi thought the real world was boring, so she turned it into an anime, complete with all the tropes listed here. It fits her character. The characters actually look like anime characters to each other, they just don't notice or care.

Haruhi is Haruhi Suyuzima
Do you have any evidence to support that absurd claim?

One of the other characters is Haruhi Suzumiya
Probably Mikuru.

Suzumiya Haruhi is a/the slider.
The Data Overmind experienced a burst of data centered on Suzumiya Haruhi. This burst of data may have come from the rewriting of the universe to include Haruhi as the universe was copied over from the previous home universe of Suzumiya Haruhi and the copy edited to conform to Haruhi's wishes. When any slider moves to a new, non-random non-target universe, a universe is created using the template of their own universe with the wishes of the slider imprinted on it. What the Data Overmind experienced was the changing of the template before it was activated, primarily to include espers but also to copy people and edit their memories where necessary to fit the new universe once the universe had been physically constructed. The giants in the closed space do not destroy reality, they merely edit the template as it lies parallel to the original. The espers use Haruhi as a link to the new universe, and are returned to the universe they normally perceive once the attempt at writing a new universe is aborted. The universe from which Haruhi and the espers hail is not destroyed in the process of a new universe coming into existence, which is evidenced by the universe returning to its original state once the closed space is reverted. The guess is supported also by Kyon of the anime and possibly original-language light novels wishing to meet a slider, as he would ot technically have met a slider if he merely discovered his own slider powers. This is neither exclusive to nor dependent upon the guesses that Kyon himself is a reality warper or a slider (or that Haruhi is the slider because Kyon is god, as mentioned above). The entity known as "Sasaki" no longer retains her powers because the version of her that exists in the current universe never had them, and she only retains the memory from her original self. It is possible that the original may one day enter the univeerse in which the series takes place, causing dissonance between the Sasaki who chose to lose her powers and did not, and the Sasaki who chose to lose her powers and may regret having "passed them on" (from her interpretation of events).

== Haruhi used her incredible powers to cause everyone in the world to create an inordinate number of AMVs dedicated to her, because the thought it would be fun watching what people came up with (and, thus, be more interesting than just WATCHING the show). Just As Planned ==

Tsuruya is a vampire.
Haruhi wished for time-travelers, aliens, and espers, so it's not too out of the league that she'd have also wished for a vampire. Thus, Tsuruya.

Haruhi is what happens when The One dies before being freed.

 * Haruhi commited suicide after that baseball game when she realized how boring her life was. The factions monitering her are not really time travelers, aliens or espers but Freed Humans from Zion, Specialized Agents and regular humans who she channeled some of her anomoly powers into since she does not have the framework undertsanding of the Matrix to properly use them herself.

The Integrated Thought Entity gave Haruhi her powers.

 * The IDTE sought to overcome the boundaries imposed by its intellectual limitations by giving a copy of its powerset to a human whose mind indicated a strong potential to use them creatively. Yuki even tells Kyon that Haruhi has data powers in line with the Entity's own abilities. The Entity and its Interfaces probably have some good reasons to keep that knowledge as closely guarded as possible, which is why Yuki chooses not to tell Kyon her group's beliefs regarding Haruhi's powers.
 * But then why didn't Yuki just tell Kyon that? There'd be no point in keeping the origin of her powers a secret. In fact, Nagato specifically doesn't tell Kyon her side's theory because it may not be the correct one. It's just their theory, one of several, and they're not so arrogant to start bragging to Kyon about it like Koizumi does. If the IDTE did indeed give Haruhi her powers, it'd be quite simple and safe for Nagato to just say "We did it."
 * My theory is that the Future!IDTE who already had the power of 'autoevolution' sent Haruhi, a humanoid interface, back in time to ensure that Present!IDTE would discover the power of autoevolution and prevent the world from exploding due to a time paradox. Along the way, she prevents another paradox by teaching the kid who discovered timetravel and inspiring him. The preface written in the collection of short stories (I forgot which book, it's when the SOS brigade was ordered to make an anthology of stories or get kicked out of the Literature Club room.)was a remnant of her memories as a humanoid interface. Her presence attracted the timetravellers, namely Mikuru who was tasked with keeping the founder of timetravel safe. How does she does so? With the assistance of Kyon, who was only told of their existence because he was close to Haruhi.
 * Twisting this slightly... Haruhi is a virus which infects the IDSE. They don't understand her and whenever the IDSE software agents get too close to her they either go knife crazy or recreate the world to protect themselves from her corruption.

The entire world literally exists in Haruhi's head.
Or, if you prefer, the story is pulling a Tommy Westphall on us. Haruhi is trapped completely inside of her own mind, and the world being created exists in order to fill an otherwise empty and disconnected existence. The S.O.S. members are dimly recognized versions of her aides and therapists. Kyon is an Animus figure (a contrasexual Jungian archetype) whose purpose is to help lead her back to reality. She tells the story through him.
 * Alternately, Kyon is the disconnected one, and Haruhi is his anima who is trying to guide him back to reality.

Haruhi is a Domina
The Integrated Data Sentience Entities are Excrucians. Yuki is a full Excrucian and Asakura is a Deceiver-shard. Haruhi's Regius has been destroyed and she has a form of amnesia. Kyon is unknowingly her anchor. This explains the events of Disappearance, as Kyon, being an anchor, was unaffected by the changes Yuki made to the world.

If Haruhi becomes aware of her powers, the universe will eventually change to be as if she always knew.
Think about it. How often have you learned something really important and simply can't imagine not having known it at some point? The idea here is that once Haruhi is aware of what she is, she'll begin to forget that she was ever unaware. Thus, the universe will become as if she always knew.

Haruhi is a lucid dreamer, and the entire universe is her dream.

 * I read an article about lucid dreams the other day, and it fascinated me. Noticing certain "dream signs" in your dreams can help you become lucid, and occasionally even control your dreams, essentially becoming a Reality Warper within your own dream.
 * As an explanation for Haruhi's powers, it could very well be that the entire series universe, is, in fact, her own dream. The reason the main cast doesn't want her to see any out-of-the-ordinary things happening is because it could possibly trigger lucid dreaming and allow her to fully control her powers with her conscious mind rather than her subconscious. And let's not forget what would happen to the rest of the universe if she were to awaken due to being traumatized within her own dream...
 * This explanation might not work with the revelation of the Anti-SOS in the later light novels (specifically how Haruhi supposedly got her powers from Sasaki), but it's still an interesting thought.

Haruhi is a modern, Japanese schoolgirl version of Alice.

 * In the second Alice book, "Through The Looking-Glass", Alice tries and tries to control her imagination and make everything normal, but can't. She ends up experiencing all the "madness" and "grows up" at the end of the book. Contrariwise [see what I did there?], Haruhi doesn't control her imagination, wants to make everything abnormal, and ends up doing exactly that. But, she doesn't experience any of the "madness" and doesn't grow up [i.e., she will always be a brat].
 * In the same Alice book, the White Knight is the only entity in the Looking-Glass World that is kind to her. Everyone else behaves either abnormally or rudely towards Alice. In Haruhi's circumstance, Kyon is the White Knight figure who is mostly annoyed, while everyone else seems to have their work and lives revolve around Haruhi.

Haruhi is Loki in female form.
This would explain Haruhi's erratic behavior. Loki was put in there by Odin for killing Baldr all those years ago, and he must have made a mistake when doing the ritual. And soon, Odin will come back and attempt to murder Haruhi!

Haruhi is an interface.
Haruhi's powers are not at all dissimilar to those of the Integrated Data Sentient Entity interfaces. They both use closed spaces, which seem to have similar results for espers. Yuki was able to interact in both cases when Ryoko and Haruhi decided to grab Kyon off for themselves. So what are the pside-effects here?
 * Haruhi is an interface who was born as a human. The other IDSE factions only caught onto this when Haruhi sent her message, and have been playing catch up ever since.
 * The other interfaces are lying about Haruhi either because they don't know or because Haruhi's ability to tap into Humanity's data manipulation powers makes her the most dangerous faction.
 * Haruhi is awakening the espers, which greatly increases the dangers that humanity poses to the IDSE.

Haruhi is the third puppet.
Yuki is transparently a puppet of aliens powers. Mikuru has been puppeted by mental restrictions. Haruhi is in one way or another the puppet of a god. All three girls in the brigade are puppets.

May the Earth rotate the other way.
Haruhi's first wish has already been granted, so how about that other wish? My guess is that she is begging Kyon to choose the other girl to make Goddess.

Haruhi is too immature to maintain the masquerade.
Why would a being who knew better pretend to be Haruhi by this point? The only possible reason is to make the other brigade members squirm, which is a rather immature attitude. Such an immature actor would have revealed herself by this point so Haruhi is not intentionally maintaining the masquerade. (Time looping out of Freudian slips is averted because Yuki is immune.)
 * Haruhi is also too bright to have missed all the clues, so she is operating under a mental block that not only keeps her from remembering the truth, but also from discovering it anew.
 * Note how Haruhi tunes out Yuki, whenever Yuki is being obviously non-human. ("Say, how can anybody type that fast? Why don't I go ask her what's up?")
 * Haruhi's mental block is weakest whenever she fears losing Kyon. (Could be the Smith factor, the first person who really talked to her, or she knows it all comes from him.)

"cold palace" where disfavored queens and concubines were banished.
The guess here is that the author intended this hidden meaning. Therefore Kyon is not Captain John Smith, he's more like Captain James T. Kirk, dealing with a goddess in diapers, until her real parents come to pick her up. (Assuming that they survived the explosion of Kypton or whatever excuse they had for dropping her in this sandbox Earth in the first place.)
 * Alternatively, her family name is a reference to the medical condition the Chinese call "cold palace".

Kyon doesn't even think the name Suzumiya, because she doesn't have it anymore.
In the timeframe where Kyon is writing the books, Haruhi has a new family name and he isn't aware if the other three have changed theirs.

The series itself is a Deconstruction of a manga/anime series gaining awareness of its Fourth Wall.
Semi-self-explanatory. Mikiru says that her era cannot travel through time to any point before the series begins - This is because the writers hadn't started writing it yet. Think Robert A. Heinlein's The Number of the Beast.

If Haruhi ever admits her feelings to Kyon, the SOS members and every other supernatural being will disappear, or at least lose their powers.
Every party appears to think this is the way to control Haruhi's powers - and it is. Sadly, this means Haruhi will focus less on wishing to see strange things and more on Kyon and her love life, and ultimately deciding that she doesn't need weird and wonderful happenings anymore. This will result in all time travellers, aliens and espers disappearing for as long as she doesn't believe in them (as much, anyway) - however, assuming she wouldn't want her friends to disappear, they may just lose their powers instead of vanishing. And to take it one step further, Haruhi may lose her own powers, too.

Haruhi will grow up to become an author.
Specifically, she will write short stories, and eventually light novels, about a reality bending boy named Haruki who meets an insecure girl who goes by the nickname Kyonko.

At some point, present day Haruhi will go back in time without realizing it.
At that point, she'll wish that she could have been granted some kind of reality bending powers by a godlike figure when she was younger. And so it will be.

None of the factions are correct about Haruhi.
She is not the God. She did not herself grant the esper powers. She did not cause the time block. And she does not offer anything unusual for the aliens. The truth is something different.

Only a Sith deals in absolutes
Haruhi favors categorical statements at the start of high school, but mellows out over the next year. Now if only she'd wish for a light saber.

Haruhi was visited on multiple Tanabatas.
She says as much when Kyon returns. That means he needs to visit her on two more years.

Tanigawa has no idea what is up with Haruhi either.
He's stringing us along for the ride, and he's enough of a pro to keep us entertained in the process.
 * Not really all that surprising since, if you read about most famous writers, they usually don't have a totally outlined detailed plan of every single thing that is going to happen in their stories. Apart from Tolkien who planned out every blade of grass in Middle Earth, most writers I've ever read about have only a vague idea of what exactly is going to happen to their characters and this can change during time.

Haruhi is the Dungeonmaster's Girlfriend
Kyon's a GMPC, but is trying to not to outshine the other characters, and is failing badly.

Haruhi allowed the events of The Disappearance to happen because of her trust in Kyon
Haruhi allowed because of her unquestioning trust in Kyon which was brought up in "The Day of Sagittarius." Haruhi knew that Kyon would.

Kyon's real name is "John Smith"
Or the Japanese equivalent of John Smith... a very, very common name which is so common that it has the same effect in Japanese that John Smith has in English. Something like Satou or Takahashi for a family name, and something like Akira or Hiroshi for a personal "first" name. When Kyon referred to himself as "John Smith", he was making a linguistic pun on his own name by using one of the most common names in English.

Haruhi and Kyon ARE Orihime and Hikoboshi
Haruhi and Kyon are the gods associated with Altair and Vega. They decided to incarnate on Earth for a giggle, wiping their minds and most of their godlike powers for the time being. Haruhi (Orihime) is still using her Goddessly powers subconsciously, however, and this is what is causing problems. This also explains why Kyon is pretty much immune to Haruhi's powers and meddling, and why the pair of them can emphatically read each others minds. Also explains the effect where Haruhi seems to consider Kyon an equal, although she continually gives him a hard time, while the other brigade members are seen are mere toys or people just there to fill a certain role.

Haruhi is set in the same universe as Chaos;Head, and Haruhi is a Gigalomaniac.
Haruhi has the god-like power to turn her delusions into reality, after all.
 * Haruhi is a gigalomaniac regardless.

Haruhi is a Tenza
Reality Warping Powers? Check, oblivious to said powers? Check. Powers start going wonky right around puberty? Well, that's what the Doctor said might happen, so check.

Haruhi died that day in Junior High
Kyon was somehow involved and so so feels responsible for the death of ordinary girl Haruhi. He therefore used his powers to reanimate her. Unfortunately he Mary Sue cursed her at the same time.

The whole series is taking place in Haruhi's Cosmosphere
Which explains why Haruhi has god-like powers, the whole thing is taking place in her imagination.
 * Yuki and Mikuru are other Reyvateils with their own Cosmospheres. Yuki is probably an Origin type. Koizumi is another Reyvateil partner like Kyon.
 * Except, these aren't the real Yuki, Mikuru and Koizumi's, just mental creations of Haruhi's based off of her memories. Only Kyon and Haruhi are real inside her Cosmosphere.