Pooh sneezing and causing Rabbit's decorations to fly onto him.
Rabbit: Why did I ever invite that bear to lunch? Why, oh why, oh Why?"
And before that, Rabbit trying to make Pooh's bottom like a moose trophy, but Pooh giggles as Rabbit draws the mouth, making it all crooked.
Rabbit: Oh Pooh, you messed up my moose!
(cut to Pooh on the other side wearing a similar expression as the "moose")
When Rabbit overhears Gopher offering honey to Pooh, he yells, "Honey?! OH NO!" He then begins to run outside, only to trip over a chair with a rather priceless expression.
And shortly after stopping Pooh from eating honey and telling him that he'll taste it for him, Rabbit leaves and then comes back to hammer a sign that says, "Don't Feed The Bear" with his own fist, saying, "DON'T! FEED! THE! BEAR!"
At the beginning of the scene, Pooh is sleeping like a baby, while on the other side, Rabbit is sitting there completely stressed with eyes wide open.
"Christopher Robin, I have come to a very important decision. These are the wrong sorts of bees!"
Pooh accidentally ripping his backside during "Up, Down, Touch the Ground".
Pooh: Oh, stuff and fluff.
Christoper Robin is asking why Pooh rolled around in the mud. Pooh says in a completely matter-of-fact way "I'm a little black rain cloud, of course." It's the way that Pooh says it that really helps to sell the punchline.
Winnie the Pooh and the Blustery Day
Pooh and Piglet are blown onto Owl's window.
Owl: Well, I say now. Someone has pasted Piglet on my window.
The rest of the scene involves Pooh and Piglet being thrown across Owl's room, while Owl is oblivious to the severity of the storm outside and keeps rambling on about his family. Hilarity Ensues.
If you pay attention to that scene, the tree falls down exactly in the direction Pooh was sitting in Owl's dining room. So, as antique and fragile as the tree was already, it might have been Pooh's fault actually, making that scene's last lines funnier.