When this author first began to take classes in theater and comedy improvisation, his motives were largely creative and social, though there was some supposition that his mathematics teaching (at a community college) could benefit as well. Students are known to tout their favorite teachers as "funny." Taking improv classes would presumably loosen him up a little and make him more confident about his stage presence, thereby helping to facilitate the occasional joke or witty aside that could make for moments of shared humor between the teacher and the class. Now, some years and many improv classes later, he has come to recognize that the art of improvising and the art of teaching share fundamental themes. In fact, he believes that they can be seen as crafts that share some fundamental rules. The "rules" involved in improv are somewhat less rigidly defined than those in mathematics, but they are rules, nevertheless, and one stands out above the others: the rule of affirmation. If an instructor wishes to develop an interactive rapport with the students, eliciting their participation and facilitating discussion, one should exhibit sensitivity to students' feelings and egos. By affirming some aspect of any student's input, one also pushes the mathematical "scene" forward, into possibly unexpected and rhetorically rich directions.