What does it mean to have mathematical authority? How does it differ from pedagogical authority? We drew upon Goffman's (1981) ideas of author and animator to exemplify modes of mathematical authority that extend beyond the authorship of ideas. Through a series of excerpts from lessons in middle-grades mathematics classrooms, this paper emphasizes the importance of two modes of animation: authority for speaking and representing mathematical ideas. These excerpts also reveal the fluid nature of mathematical authority within a classroom. Implications for teaching are discussed.