via Steven, a page that finally reveals the truth about Calvin and Hobbes:
Mr. Bun is the only real character. In case you’ve forgotten, Mr. Bun appears only once or twice in the entire run of the comic, as Susie Derkin’s stuffed rabbit. Unlike Hobbes, Mr. Bun shows no sign, within the comic, of ever being “real.” (“Mr. Bun seems comatose,” comments Hobbes, after attending a tea party with Susie and Mr. Bun.) Naturally, this is strong evidence that Mr. Bun is the only “real” character, and everything else is occurring in Mr. Bun’s imagination. If Mr. Bun doesn’t actively particpate in his expansive fantasy world, it’s only because he prefers to just sit back and admire his work.
I suspected as much all along.