In the classic comic tradition of sidekicks, Hobbes represents Calvin's potential maturity and externalized conscience. A comic about a young boy throwing slushballs into a neighbor girl's head would be sad and trite without Hobbes there to wisely tease him, "You think she's cute, right?"

From everyone else's point of view, Hobbes is Calvin's stuffed tiger. From Calvin's point of view, however, Hobbes is an anthropomorphic tiger, much larger than Calvin and full of his own attitudes and ideas.

Hobbes' intangibility is called into question, however, when he pounces on Calvin (often leaving Calvin disheveled) and in one incident, ties him to a chair in such a way that his father is unable to understand how he could have done it himself. Also, in a very early strip, Calvin says that Hobbes ate a classmate of his (and Hobbes seems to verify this.) No other reference to Hobbes doing anything to another person is ever made.

Hobbes is much more rational and aware of consequences than Calvin, but seldom interferes with Calvin's troublemaking beyond a few oblique warnings—after all, Calvin will be the one to get in trouble for it, not Hobbes. Hobbes also has the habit of regularly stalking and pouncing on Calvin, most often when Calvin returns home from school. Hobbes is sarcastic when Calvin is being hypocritical about things he dislikes.