My Winnie-the-Pooh Epileptic Tree
On TVTropes, they have a term called "epileptic tree" for off-the-wall fan theories. At dinner last night, I came up with one of my own. Lest anyone be concerned, this is a joke...
Winnie the Pooh is really about invasive animal species, with the kickoff of many of the major plot points likely being a mass escape from a circus or zoo.
When I was little, my mother took me to a Winnie the Pooh show at the Atlanta Center for Puppetry Arts. The storyline that I can remember involved the arrival of Kanga and Roo at the 100-Acre Wood and the reactions of the other residents of the Wood to the new arrival. I remember one of them saw a bottle Kanga had with a skull-and-crossbones on it (some kind of medicine or household chemical, I imagine) and telling the others it had the bones of a dead animal on it, to their general fright.
Winnie the Pooh and the Blustery Day, which I watched a lot when I was a kid and even brought to my preschool class at Mount Bethel United Methodist Church for my classmates to watch (that was when I lost my first tooth as well), also depicts Tigger as being a new arrival to the 100-Acre Wood. He acquaints himself with Pooh (in his typical fashion of jumping on him) in the middle of the night one night and claims the most wonderful thing about "tiggers" is that he is the only one.
Author A.A. Milne was British, so I'm assuming the 100-Acre Wood was in England somewhere. Neither tigers nor kangaroos are native to England, so Kanga, Roo, and Tigger would had to have been introduced from elsewhere.
Perhaps there'd been an escape from a circus or zoo and the three of them made their way to the Wood from there. According to Wikipedia, there are wild colonies of red-necked wallabies living in Scotland and France (and there used to be a population of England that apparently died out), so there is precedent for Kanga and Roo.
As far as Tigger is concerned, one theory behind the phantom cats like "the beast of Bodmin Moor" is that they're escaped zoo or circus animals that have successfully established themselves. Not only would that explain Tigger, but it could also explain the "jagular" from The New Adventures of Winnie the Pooh--although we never actually meet a "jagular," the other characters seem absolutely terrified of it. Perhaps Tigger sustains himself with fish from the river and isn't a danger to the others (except perhaps by playing too roughly with them), but the jaguar, another escapee from the zoo, has a preference for bigger game (like Piglet).
The Heffalumps, who have actually appeared in some of the more recent Winnie the Pooh materials like Pooh's Heffalump Movie, might also be escapees from a circus or zoo. Given how we don't actually meet any of them until relatively recently (aka the newer stuff), perhaps they and the "jagular" came from a more recent zoo/circus escape than Tigger, Kanga, and Roo. Given the release dates of the Pooh materials, the original three established themselves in the 100-Acre Wood sometime in the 1960s, while the Heffalumps and the "jagular" escaped during the 1990s.
If I wanted to get really dark, I could suggest a Winnie the Pooh movie in which the British animal-control service invades the 100-Acre Wood to collect the animals that don't really belong there. It'd be like The Secret of NIMH in which NIMH's discovery of where the escaped intelligent mice are living is a major plot point. Given how an escaped family of elephants would be a much bigger deal that kangaroos or even a couple of big cats (I don't recall major efforts to hunt down "phantom cats," although they might not actually exist), it could be a direct sequel to the Heffalump movie.