¢Calvin the Salesman is a running gag where Calvin sets up a booth (usually made from a cardboard box) to sell some product. Calvin has used many different ideas over the years to try to earn money, but of course, they all fail miserably.
Calvin has run several lemonade stands over the years. The thing about his lemonade, is that it is simply a Lemon dropped in sewage water. He sells a cup for $15. Susie tries to tell Calvin about this, however, Calvin replies with lame excuses though, and eventually, Susie normally just gives up, and goes home.
Calvin once made an insurance booth. When Susie made fun of it, asking who would buy insurance from him, he shot at her with a sling shot.
A swift kick in the butt
This was Calvin's least successful business. He didn't sell one, and seemed fairly surprised that it wasn't successful, since it seemed everyone he knew needed one.
Once, Calvin set up a booth labelled simply "Life 5¢". Susie gave Calvin a nickel, only to be told that she would receive nothing. "That's life," Calvin told her. She responded with crushing the booth, and knocking Calvin to the ground.
Calvin once gave out great ideas. Calvin's mom bought one, and the idea Calvin gave her was "Buy some more!"
Calvin made a "Happiness 10¢" booth, where it's basiclly a water balloon in the "kisser." When Hobbes asks whose happiness is this, Calvin said, "Who went to all this trouble?!?"