Informal science education institutions play an important in the public understanding of science and, because of this are well‐positioned to positively impact science teacher education. Informal science institutions (ISIs) have a range of affordances that could contribute to learner‐centered science teacher identity development. This article describes research from a clinical experience in a museum where teacher candidates engaged visitors in learning dialogs around objects on a moveable cart in an exhibit. We describe how working in informal settings and learning to use the affordances of that setting supports aspiring teachers to connect theory to practice in ways that developed Spielraum in that is student‐centered, responsive to the needs of learners, and allows for the imagination future selves and classrooms that are conducive to maintaining these identities. This research supports the critical role that ISIs could play in teacher education, especially during the clinical phase where teacher candidates are forming initial notions about their identities, about the self who teaches. © 2015 Wiley Periodicals, Inc. J Res Sci Teach 54: 121–138, 2017