Group brainstorming is a popular ideation method for design teams, yet brainstorming outcomes vary greatly. The method depends on individuals working collectively to generate ideas, and so group dynamics determine whether the method succeeds or fails. This paper explores how interaction designers used techniques from theatrical improvisation, or improv, to adhere to the rules of brainstorming thereby enhancing group interactions while collaborating. The usefulness of improvisation for brainstorming stems from the similarity of the goals of improvisation and brainstorming, the similarity of the recurrent problems that actors and designers encounter when collaborating, and the distinctness of the ways each have devised to resolve the problems that block the group's performance. This paper reflects on the individual- and group-level outcomes for design students and practitioners while brainstorming.