In this essay we argue that metaphor and language play generally should be analyzed in the context of actual conversations, not as a peripheral or incidental part of the discourse, but as an integral part of both topic-centered and relational work. We examine several instances of playful metaphor, humor, and irony that occurred during a one-hour focus-group discussion among a group of scientists discussing their role in communicating about science with laypersons. During the course of this discussion, word play, humorous insults, and the elaboration and reconstruction of metaphorical idioms are used for a variety of purposes, including reinforcement of group boundaries, re-constitution of the group's assigned task, and joint development of a complex set of ideas about group members' identities as scientists working in a publicly-funded lab. Throughout this conversation the social structuring and relational functions of playfulness and metaphor interacts with the accomplishment of the purposes of the conversation. We argue that analysis of language play, humor, and metaphor is strengthened by attention to the purpose of the talk and, conversely, understanding how the purpose of talk is accomplished is strengthened by attention to the participants' use of playful, metaphorical, and humorous language.