Dilbert/WMG

Loud Howard is not what he seems.
In 'Ethics' Loud Howard points out that he always votes for the tallest politician, believing that they will inevitably be the most successful. Now, what other race idolizes tall people? This explains some of his strange quirks and beliefs.

The Garbage Man is the Avatar
He seems to have many of the same philosophies as the Avatar.
 * Alternately, he's the Avatar.

Wally is George Costanza
They have the same hair style and the same glasses and generally the same attitude on life. It's unknown why George decided to change his name, but it's possibly part of a zany scheme to get hired after spending a year in jail. He's figured out that everything he does is basically doomed to failure, so solves this problem by never doing ANYTHING.

The Garbageman is related to Dilbert.
They do look similar in facial structure and body shape. And he hangs around Dilbert a lot. And he was the one who cloned Dilbert after he died. He lied when he said he cloned Dilbert from Dilbert's garbage -- he was the genetic source... We never see any other candidate for Dilbert's father, do we?
 * Dilbert's Father is referred to in the comic by both Dilbert and Dilmom. He went to an All-You-Can-Eat restaurant ~20 years ago, and hasn't left because he hasn't eaten all he can eat yet. In the TV series, Dilbert actually braves going back to the mall and gets to see him again for a few minutes.
 * The Garbageman took DNA samples of the garbage outside an All-You-Can-Eat restaurant. The rubbish had traces of a man's saliva on it. The Garbageman used them to grow Dilbert. He later informed Dilbert's "Father" of this, but instructed him to mislead Dilbert if he ever came searching. Dilbert's "Mom" is an actress hired by the Garbageman. The Garbageman is actually a multi-billionaire Mad Scientist, who only pretends to be a custodial worker in order to observe his creation every now and then.

The Garbageman is Dilbert.
He came from the future for reasons unknown. For the nitpickers, if Dilbert dies, how did he come from the future and then clone himself? Dilbert doesn't die until the Garbageman unintentionally alters the time line by coming to the present. So Dilbert can survive to travel back in time as the garbageman and clone himself.

The Pointy Haired Boss is neither an idiot nor incompetent. It is all part of his plan.
The PHB was originally competent and just downright sadistic. Then he suffered Flanderization into being an idiot.... most of the time.

But if he were really an idiot, then he wouldn't be able to not be one. So he isn't.

He has three modes: evil, sociopathic, and Obfuscating Stupidity to keep his workers fooled. When he still shows signs of intelligence, he's in his evil mode.

When he's merely being sociopathic, he comes off as an idiot, but in fact doesn't care (either about what he's dealing with or how he looks).

He pretends to be an idiot because his employees, thinking he won't understand them, tell him things he would never know otherwise. This is his way of knowing everything is going on.

Note the Wally vs PHB performance reviews. Wally is the intelligent but apathetic employee; the PHB is almost always forced to revert to being evil or sociopathic because Wally knows his game. PHB drops his act privately around Wally more often because Wally is too apathetic to tell.

Either that, or PHB is Wally's Worthy Opponent.

Dilbert's company is the world's third largest producer of hard core pornography
This is why we are never quite told what products Dilbert's company makes.
 * No, they make technology. Something to do with computers. That's not to say it isn't of a sexual nature. Nearly all of their products have a hole or rod and not much else, and so they could be a producer of computer-linked sex toys.
 * Given that a reference was made to making missile guidance chips at one point, there is something ominous about that guess.
 * In the animated series, they made exercise machines.
 * "Exercise machines"? Anyway, there's nothing that says Dilbert's company can't keep its different product lines censored and classified.
 * Pro-"porn company" example: The Marketing department. They drink wine and kill unicorns, not to mention giving Dilbert the horn (not a euphemism). Although it does get kind of creepy when you recall the arcs where employees were encouraged to sell to their families, and Dilbert's mom knew more about the product than he did.
 * Well, at one point Wally attempts to trick the PHB into letting him "test" their servers by downloading "large files" from the "busiest sites on the Internet", which, as he mentions to Dilbert a bit later, means looking at porn. (The PHB doesn't let him.) You'd think that if they made porn that Wally wouldn't need to do that. Also, Tina is notoriously touchy about these sorts of things. It seems to me like she'd be the sort of person who's opposed to porn.
 * Support for this series comes from a recent strip, where two of the three categories for possible names for the new product are "funnier nicknames for partnerless loving" and a related "general area of the human body." So they may very well sell vibrators.

Dilbert lost his mouth when he first got hired by the company.
Every other human has a mouth, and he had a visible mouth as a child, but now his mouth only appears under extreme duress. Genetic experimentation is the only answer!
 * Sounds more symbolic.
 * Can't it be both?
 * Then why aren't there more people in the company without mouths?

Dogbert already rules the world.
He just has Scott Adams publish the Dogbert New Ruling Class paper to placate the people who were too smart to get newspaper ink on their nose, but not exactly DNRC material.
 * In one newsletter, Adams claimed that Al Gore is a robot mech being piloted by Dogbert. Since Gore lost the election, it seems Dogbert failed. Then again, he has won both an Oscar and a Nobel since then, so maybe he's more influential than we thought...
 * He doesn't want to win, remember? He's won it before and given it up out of boredom. Maybe he threw the election to preserve the fun of the chase.

Dogbert is Dilbert's split personality
Because how likely is it that Dilbert really shares his house with a talking dog?
 * But everybody else sees him too.
 * Everyone saw Tyler Durden also.

Dilbert is Garbageman's Nobody
Because it explains why they look similar and why Dilbert has such a boring personality.
 * That would make the Garbageman a Heartless... but he hasn't been shown as at all animalistic or cannibalistic, which means he didn't have any darkness in his heart, which would mean that....

The Garbageman is an eighth Princess of Heart
A male one, obviously, but the only title we've been given for that condition is feminine. A logical extension of the above guess.

Alternatively, Dilbert is Garbageman's Fetch.
Garbageman is too nice to kill Dilbert and steal back his old life, and let's face it, he has a much more satisfying life as an anonymous garbageman, anyway.

The strip takes place in Hell
This is pretty obvious, really. The entire world is a bureaucratic, oppressive nightmare. The Company is filled with psychotic monsters. The Status Quo Is God - anyone who is promoted or fired eventually returns to normal (Asok, most recently acquired of the damned, has been a naive intern for more than five years). The main characters (the damned) are twisted personifications of the Seven Deadly Sins - Wally is slothful, Alice is wrathful, Dogbert is prideful. Dilbert is more or less a husk of a person, constantly downtrodden, rejected socially and continually mocked and tortured in business. He used to have hobbies, but as his time in Hell has gone on, his home is featured less and less, as he is slowly sucked into the Company offices.
 * The accounting department is literally a giant cavern complex filled with trolls whose stated goal is to erase reality (it's never explained how Accounting is connected with the main building - possibly, it's the basement). At least, that used to be its purpose; then Dilbert killed the androgynous, witch-like leader. Now Accounting doesn't do much besides steal souls, insult people, and (apparently) rip people's heads off during budget season. A cave full of trolls who rip heads off. Sounds like Hell to me.
 * The engineers, as mentioned before, are the damned. The Pointy-Haired Boss is the "main demon" torturing them; they face him every day, and it's been conclusively proven or outright said again and again that he detests every one of them and would like nothing better than to see them dead.
 * Human Resources is run by Catbert, a talking cat (!) whose entire personality is based around his hobby of making policies to hurt the workers. Sounds like a demon to me. In one strip (with Scott Adam's commentary), he actually orgasms multiple times to the thought of employees being hurt.
 * Besides the Company and its executives, Dilbert and the other engineers are often bombarded by minor devils - random, surreal coworkers, named after their flaw and designed to torment. Loud Howard, Parakeet Man, Techno-Bill, Hammerhead, Topper, Buff Bufferson, and Bottleneck Bob all have one purpose and never deviate. Their names even sound demonic in a playful, childlike kind of way.
 * Alice has made the Company millions of dollars in cash over the years and has had over ten patents in her name. The Company has refused to recognize her achievements, forcing her instead to work harder and harder. This continues until she becomes a husk of a woman, at which point she will be replaced by Tina (see below)
 * The Company has been in business for decades now, and absolutely no staffing positions among the main characters have changed despite the continual threat of reorganizations and the typical threats from the PHB to fire people. Apparently, he prefers to keep Dilbert and co. is constant fear. (Every other character comes and goes.)
 * Carol has been trying to kill the PHB for years, and despite her brutal methods (including shipping him to third world countries with revolutions going on wearing a target on his shirt, teaching him to be helpless in every basic task, and shooting him with a crossbow) he remains perfectly alive and healthy. She's also still his secretary, and she is walked over more or less any time she appears.
 * One short arc was about another "generic guy" who grew a beard out of his forehead. Alice pushes him down a flight of stairs, he dies, and demon possess his body. She stabs him with dozens of pens in an attempt to destroy his heart, and he stays alive since his heart is "the size of a raisin". Enough said.
 * Scott Adams has stated that he was worried about getting called racist because of Asok's inevitable flaws (every character in the strip has serious flaws), so he picked out a small flaw that will go away in time: Asok is naive and inexperienced. He has been that way for years by now.
 * Tina is easily offended and has a quick temper - in time, she will have been beaten down by Hell to the point where she's really just another Alice.
 * "Run, Jennifer! It's too late for me but you can still save yourself! RUN!"
 * ...damn it, now I want to make a Jack crossover.
 * PHB can summon demons (it is not the only time).
 * I seem to recall that he's Phil's brother, according to a comic where Heck filled up and the Prince of Insufficient Light had to house a new tenant in Dilbert's cubicle.
 * Don't forget Mordac, summoning the Y 2 K Demon. In fact, Mordac even sounds like the name of a demon.
 * So what is Dogbert's role in all of this?
 * A vainglorious, megalomaniacal man, long since dead, sent down to hell and twisted into the shape of a common dog. He can still speak and think rationally, and he must forever live with the knowledge that he is no longer even a man - only a domesticated animal, constantly subservient to humans. He aspires to rule Hell, but must always give up power when it is reach, as part of his punishment.
 * There was a storyline, very early on, where Dilbert was killed by Mother Nature as an example; demonic stuff and hellish work conditions didn't show up until afterwards. Presumably, his "revival" shown on-panel was actually his arrival in Hell.

Wally and Alice have a well-disguised Belligerent Sexual Tension relationship
Considering all she's put up with without killing him, there's got to be something there.
 * I always thought that this would be in the cards should Scott Adams ever decide to pair up his characters. Which he wouldn't, but if he did I assumed it would pretty much have to go that way. Maybe Dilbert would end up with Tina -- there was even an arc in the strip in which she had a crush on him and he didn't notice. And the PHB and Carol are practically already married.
 * I always liked the idea of Wally and Tina ending up. There have been a couple of strips that could be interpreted with no dialogue or mannerism changes to show that they have crushes on one another. It'd be cute and also an entertaining mismatch, considering how Tina sees imaginary sexism everywhere and how sexist Wally actually is.
 * ...Wow. He's the only person where she'd be right.

The Jowly Boss got fired.

 * And replaced with the Pointy-Haired Boss we all know and love.

The World's Smartest Man is a garbageman because...
Seriously. Time, funds, people to educate and talk to, so as to avoid stagnation...it's a pretty good deal.
 * The pay's pretty good.
 * The hours are good (assuming he's a morning person).
 * He gets to talk to a good cross-section of the population.
 * He enjoys it.
 * I have a theory that, like a lot of incredibly smart people, he doesn't have the social skills to get a better job, though admittedly there's little in-comic evidence for this.
 * The canon explanation is that the reason can only be comprehended by the world's smartest human, the garbageman.

Dilbert is what Charlie Brown would be like if he'd have grown up
The Dilbert universe is what the future Peanuts universe would have been like. Charlie Brown would eventually grow up and work for a company that neither cared or appreciated him. He still is rejected by women and has terrible luck, despite what a nice guy he is. Snoopy would eventually grow hardened and cynical, discarding his life of idle imaginings and instead dedicating himself to conquering the world. Alice is Lucy, while Wally is Schroeder, who neglected his talents and wasted his life instead of achieving his full potential. Ratbert is Woodstock (he could fly in one strip), Ted the Generic Guy is Shermy, Catbert is the cat next door and Asok is Rerun. As for Linus? The Garbageman, of course.
 * Then who's the boss?
 * Dammit! Forgot about him. Uhh...Violet? No, wait, that makes no sense. Uhh...
 * The human persona of the kite-eating tree.
 * The theory's Jossed. In this strip, Dilbert mentions Charlie Brown, meaning the two are in fact separate people.

Dilbert works for Activision.
What other company could be so evil, shortsighted and ruthless?

Dilbert works for the Outer Church.
The company is an evil megacorp that regularly employs demons, eldritch horrors, and seems to take an active roll in crushing creativity and the human spirit. Dilbert is one of the minor drones working for the Outer Church, and their branch is so completely incompetent that the Invisibles haven't bothered crushing it yet.

Dilbert works for Pentex.
Similar to the above WMG, Pentex is an evil corporation that regularly uses elder horrors from beyond the void to achieve its goals of achieving universal annihilation. Wally is possibly even a Fomor, with his completely inhuman nature.

Dogbert and Catbert are arch enemies.
Due to Animal Jingoism this would certainly make sense, especially since the only known time they met each other, Dogbert ordered Bob to give Catbert a fur wedgie...in fact, if there was a movie based off of Dilbert, this war would probably be important to the plot.
 * IIRC, Dogbert was the one who originally hired Catbert during one of his corporate takeovers.
 * What's to say he didn't begin to hate him after a while?