Stands for Get Rid of Smily Girls. It is a secret club formed by Calvin and Hobbes. Each member furnaces many roles. Calvin is Supreme Ruler and President-For-Life, and Top Scout, and others. Hobbes is President and First Tiger as well as Club General Secretary. The club typically meets in a treehouse in Calvin's yard.

GROSS activities usually involve annoying Susie Derkins. Other names suggested during chartering were the Hobbes Fan Club and the Sinister Icy Black Hand of Death Club.