The club has only two members , Calvin and Hobbes . Hobbes often openly expresses romantic feelings for Susie , much to Calvin 's disgust . Calvin starts a `` club '' ( of which he and Hobbes are the only members ) that he calls G.R.O.S.S. ( Get Rid Of Slimy girlS ) club , and while holding `` meetings '' in Calvin 's treehouse or in the `` box of secrecy '' in Calvin 's room , they usually come up with some way to annoy or socially maim Susie , most of which backfire on them completely .