 When the scene includes any other human, presumably they see merely a stuffed animal, usually seated at an off-kilter angle and blankly staring into space.The true nature of the character is never resolved, instead as Watterson describes, a 'grown-up' version of reality is juxtaposed against Calvin's, with the reader left to "decide which is truer".Hobbes is based off a grey tabby cat named Sprite that was owned by Watterson.