Winnie the Pooh/WMG

The Hundred Acre Wood is capable of changing its geography to fit the fantasies of its inhabitants.
It is the only possible explanation for what happens in the direct-to-video movie Pooh's Grand Adventure: The Search for Christopher Robin. The end of the movie reveals that all of the frightening things that Pooh and his friends encountered while they were looking for Christopher Robin really weren't that scary at all (the "giant cliff" that they actually fell into was just a few inches high, for example). This would imply that either they were all having the same hallucination or that the forest itself changes in response to their expectations. They were afraid, and so the forest became more frightening. This also explains how their journey out was so much longer than the one back.
 * So A Wizard Did It?
 * Or maybe it's just outside Springfield. Or inside it, as necessary...
 * The Hundred Acre Wood changes all the time -- it seems to have a different layout in every installment of the franchise.
 * It could be a bit of gnarly ground, where the geography corresponds with your emotions.

Rabbit eversed.
The forest starts becoming more disturbing after Rabbit takes command around the Upside-Down Rock, and goes back to normal in the Eye of the Skull. Both times, Rabbit is showing intense emotion: frustration at Pooh's incompetence at the rock, and terror induced by Christopher Robin's shadow in the cave. Possibly, there are eversion points in these areas, and Rabbit unconsciously uses them.

Christopher Robin is actually several different kids that have been amalgamated into a singular entity in the memories of the animals of the Hundred Acre Wood.
The franchise actually happens roughly in real time each Christopher Robin we see is really a different kid coming into the woods to play with the immortal stuffed animal inhabitants. The stuffed animals are unaware that humans age and assume all of the kids are Christopher Robin the original kid to come into the woods and the kids are all too polite too correct them.

Tigger is Hobbes's father.
Actually, credit where credit's due and all that, this isn't my theory. Norwegian author and mythologist Tor Åge Bringsværd (who re-translated the Pooh books to Norwegian back in The Nineties, as the translations from The Fifties and Seventies were a bit of a mess) claims this in his intro to the Norwegian translation of The Essential Calvin and Hobbes, but I thought it was a fun enough theory to mention here.
 * Combined with the below WMG, this implies that not only do Winnie the Pooh and Toy Story share a universe, but so does Calvin and Hobbes!
 * But then why does Hobbes move around Calvin when the Toy Story toys don't move around people?
 * It's revealed in the very first Toy Story movie that toys can move around people if they choose, it's just that it's "against the rules" for them to do so. Maybe Hobbes just doesn't bother to follow the rules, or somehow considers Calvin an exception to them.

A possible Happy Ending:
One year Calvin's parents took him and Hobbes on vacation to England, where they met Christopher Robin and Pooh playing in Hundred Acre Woods, and the four of them, plus Piglet, Owl, Rabbit, Tigger, Kanga, Eyore, and Roo, stumbled into an endless recursion of time, and they've been playing there ever since.

The franchise takes place in the same universe as Toy Story.
This occurred to me while lying in bed and it boggles the mind that my fellow tropers have not made the connection. What if all of the stories/episodes/movies/etc. were "play sessions" ala the opening of Toy Story 3? Perhaps Christopher Robin, like Bonnie, includes himself in the adventures occasionally and simply ignores the, shall we say, fourth wall of the play to a certain extent to accommodate any "injuries" the toys sustain. This also tidily solves the problem of the wood changing about constantly.
 * Pooh'sGrandAdventureTheSearchForChristopherRobin therefore, may be Christopher confronting his fears and insecurities about starting at school/a new school/etc. through play. The times when the toys actually interact with CR's home without him are when he's not around.

Kanga and Tigger will wind up in a relationship.

 * She's a single mom. Tigger takes good care of her son. Do the math.
 * D'awwwww.
 * Uh... or eeew, considering that Tigger is Kanga's adopted son in the original books.
 * They never really took that "adopted son" thing into the movies. In The Tigger Movie they showed him living in a treehouse by himself...but, based on the books, I'd always imagined that he was kind of like a teenager with his first apartment.

Ther refers to the male organ.
This information is, after all, the child's response to his father's question about the supposedly feminine name, and it would certainly explain the author's reluctance to explain further.

'Hunny' is analogous to alcohol.
Consider Pooh's devastation at learning he has no more of it, and also consider the Heffalumps and Woozles, some of whom are literal Pink Elephants!
 * Mead?

B'loon (from the 2011 movie) actually is sentient. And a bit of a Jerkass.
B'loon knows exactly what he's doing, and what he's doing is deliberately messing with everybody. Look how he without effort reduces Tigger to frightened whimpers, keeps Eeyore from enjoying a nice thistle, scares the living daylights out of Piglet, and as his main Xanatos Gambit manages to get all the animals to fall into the pit. Only to fly off for "help," so that he can grab all the credit for himself, become the hero of the day and snatch the prize honey away from the disappointed Pooh. What a jerk.

Owl is the Big Bad of the 2011 film.
Owl's ultimate goal is to find someone to read his memoir to in order to fullfil his self-indulgent needs. He figures that Pooh is the most easily manipulated, so he sees to it that Pooh has no access to honey by way of taking all of Pooh's personal honey in the middle of the night (thus giving Pooh a reason to leave his house at all), stealing Eeyore's tail and making sure that the best tail choices in the contest go to other characters so that THEY would get the pot of honey instead of Pooh, and making up the story about the Backson so that everyone would be out looking for it all day and Pooh would be as hungry as possible by the end of the day. Owl makes the only honey accessible to Pooh the honey at his own house, and offers Pooh honey on the condition that he sit and listen to him read from his autobiography. This all makes Owl a Magnificent Bastard.
 * I find it amusing that this the ceiling of evil-ness in the pooh universe.
 * Please. "Poohniverse".

The Backson is a Monsters Inc. Scarer that got suck in the human world.
Was I the only one who thought he looked like a character form Monsters Inc., maybe he was a top scarer before, who through an accident got locked outside of a closet in England, and decided to roam the 100 Acer Woods to find a way home.

Pooh is a Time Lord
And his hunny pot is his TARDIS, and we have proof...

Eeyore wasn't always a donkey
Originally Eeyore was a real boy but then after a trip to Pleasure Island, he was turned into a donkey. Being a donkey that could still talk, Eeyore wasn't sold off to slave labor right away. Being smart enough to figure out how to escape, Eeyore left the Island, only without a tail. Also, the magic that turned Eeyore into a donkey is also what has kept him alive for a long time, making his life long and agonizing.

Tiggers are a clan.
Tigger isn't the last of his species, he could just be the last surviving member of a clan known as Tigger...all the other members being dead (probably by the hands of one of it's own) not unlike another clan...