Roo and Gopher pull Eeyore's tail off in the process of trying to pull Pooh out of Rabbit's front door. However, when Eeyore is seen at the honey tree immediately following Pooh's extrication (and subsequently getting stuck again in the honey tree), his tail is back on.
When Pooh calls into Rabbit's hole, you see Rabbit put dishes on a rack which subsequently disappears and reappears between shots.
When suggesting how long it will take for Pooh to thin down, Eeyore's tail bow flashes back and forth between two slightly different shades of pink.
When Pooh is stuck in Rabbit's hole, Christopher Robin's socks (short/long) change sides between shots.
At the beginning of the feature, Pooh's door is seen from the outside opening on a hinge on the right side, while in a later scene, the hinge is also on the right side (which means it has changed sides)
When Rabbit turns in his chair to try to avoid seeing Pooh stuck in his door, he quickly glances to his mirror while he says "Oh no, there it is again!" At this point, only Pooh in seen in the mirror's reflection, but not Rabbit.
After Pooh gets stuck in Rabbit's door, Rabbit sits in a chair and hums, but the hum is in Pooh's voice.
Just after Pooh comes out from behind the gorse bush and starts thinking again, his mouth isn't moving when he says "Think, think, think".