Improvisational theater is mainly associated with comedy. But why is it so? In order to answer this question, I will examine three main philosophical theories of humor and show how the mechanisms that underlie those theories are constitutive part of the creative process of collective improvisation itself. In other words, I will argue that collective improvisation, through its core properties (polyphony, unpredictability and processuality), can provide the improvisers with many comical resources that can then be more or less actively exploited to create funny situations. As a support for my argumentation, I will discuss several examples taken from a series of shows that took place in Washington D.C. during FIST 2017 – a yearly competition of improvised theater. As such, by engaging with both philosophical theories of humor and concrete examples of live improv shows, this short paper will hopefully lay the ground for an aesthetic of improv comedy – a genre of growing importance in contemporary theatrical practices that has only received too little attention in philosophical aesthetics.