of all the stuffed idiots that inhabit The Hundred Acre Wood, Eeyore is the only one that knows that he is really just a child's toy. he gets quite gloomy at times since this is a hard reality to bear alone. the other stuffed animals' minds can not comprehend that their universe is a figment of Christopher Robin's imagination. Eeyore knows that there is something much larger and greater outside of his reality that he just can't quite grasp.

being powerless to control his destiny can make him turn from gloomy to outright cranky. here's an example :

from "The Pooh Book of Quotations" by A. A. Milne

"Oh, Eeyore," began Piglet a little nervously, because Eeyore was busy.
Eeyore put out a paw and waved him away.
"Tomorrow," said Eeyore. "Or the next day."
Piglet came a little closer to see what it was. Eeyore had three sticks on the ground, and was looking at them. Two of the sticks were touching at one end, but not at the other, and the third stick was laid across them. Piglet thought that perhaps it was a Trap of some kind.
"Oh Eeyore" he began again, "just----"
"Is that little Piglet?" said Eeyore, still looking hard at his sticks.
"Yes Eeyore, and I-----"
"Do you know what this is?"
"No," said Piglet.
"Its an A."
"Oh," said Piglet.
"Not O, A," said Eeyore severely. "Can't you hear, or do you think you have more education than Christopher Robin?"
"Yes," said Piglet. "No," said Piglet very quickly. And he came closer still.
"Christopher Robin told me it was an A, and an A it is -- until somebody treads on me," Eeyore added sternly. Piglet jumped backwards hurriedly, and smelt at his violets. "Do you know what A means, little Piglet?"
"No, Eeyore, I don't."
"It means Learning, it means Education, it means all the things that you and Pooh haven't got. That's what A means."
"Oh," said Piglet again. "I mean, does it?" he explained quickly.
"Im telling you. People come and go in the Forest and they say, 'Its only Eeyore, so it doesn't count,' They walk to and fro saying 'ha-ha' But do they know anything about A? They don't. Its just three sticks to them. But to the educated---mark this, little Piglet--to the Educated, not meaning Poohs and Piglets, it's a great and glorious A. Not," he added, "just something that naybody can come and breathe on."