his best friend

Well, that's one of the correct answers.

Hobbes routinely pounces on Calvin when he comes home, hard enough to knock his socks off, apparently doing significant damage, or at least getting his clothes dirty. See It's a Magical World for a slow-motion replay of an attack. The collection Homicidal Psycho Jungle Cat is named after a Sunday strip in which Hobbes attacks Calvin on his way back to bed from getting a drink of water.
Artwork © Watterson/UPS; click for notice.