Calvin's best friend is his stuffed tiger, Hobbes. Hobbes' first appearance in the cartoon is when Calvin captures him in his tiger trap:
Hobbes exists in two dimensions: reality and fantasy, and the last is actually the most "real"... Hobbes is a normal stuffed tiger, without any functioning vital parts. But, when the two friends are alone he turns into a lethal and man-eating tiger, which only Calvin knows how to control. Even if Calvin thinks of Hobbes as a constant living creature, he is the only one capable of communicating with the tiger. Together they have a fantastic time, and Calvin really doesn't need any other friends.
Even if they are best friends, Hobbes constantly manages to fool Calvin. However, in reality it has to be Calvin fooling himself... Despite this paradox, Hobbes' humor and sharp comments, has to be considered his own. Hobbes' main task in life is to please, surprise and play with Calvin. His favorite hobby is to attack Calvin each day when he comes home from school. Sometimes Calvin forgets this surprise, but most of the time he is painfully aware of what is going to happen. He is seldom smart enough to prevent it though...
This leads us to the complex of Calvin's character. On one side he exceeds all grown-ups in the cartoon with his logic, his knowledge of foreign words and his (sometimes) mature comments. On the other side he can be so much of a child, that if someone tells him that 3+4= 1000000000, he believes it to be true!
The problem, for some readers, is that there is no logic in strips when Calvin is caught in a situation where it is impossible for himself or anyone else to have contributed. Calvin's explanation to these incidents is simple, Hobbes is responsible! This is of course totally unreasonable when we know that he is nothing but a stuffed toy animal. This means that Watterson leave it to the readers to accept a fact that in reality is inexplicable.
Hobbes is proud of his nature and feels above humans. The ideas that his best friend comes up with are not always as realistic as he wishes them to be. It is therefore not seldom that Hobbes, with his deeper mentality, protests. Of the two, Hobbes is the most calm, and he is often the first to back out when Calvin's ideas is a threat to life and health.
Calvin often uses Hobbes to acknowledge his true feelings for Susie. Hobbes often accuses Calvin of being in love with her. This is a fact the little six year old strongly denies! Hobbes however, is fully aware of his friend's warm feelings for their female neighbor.
Calvin also uses Hobbes to do the things he hates, for example bathing and doing homework. He is also good to have around when life is hard on Calvin. Very often he has to sit and listen to Calvin's problems and complaints; and he tries to help the best he can.
The two friends have founded their own secret club, G.R.O.S.S. (Get Rid Of Slimy Girls) Calvin's lust for power vents itself in this club, as he has appointed himself as dictator for life! As the only regular member of the club, Hobbes is the only one that Calvin has the chance to rule over. (A fact that is a big relief to most people...)
According to Calvin, all girls are slimy, and they are therefore not allowed to be members of the club. If girls should have access the whole idea of the club would vanish, as this is nothing but a systematic persecution of girls.
The last weeks before Christmas is probably the hardest time of the year for Calvin. He believes that Santa is extra observant in this period, and therefore he tries the best he can to behave in such a manner that he will get everything on his wish list for Christmas. Calvin's wish list normally consists of at list 40 closely written pages, where he wants to have everything from heat seeking missiles and flame throwers to battleships!
These last weeks of the year Hobbes tries the best he can to persuade Calvin into doing things that will make a bad impression on Santa. Some of the temptations that Calvin usually can't resist, is throwing snowballs and teasing Susie...