Examining critical incidents in the mathematics classroom is a useful way for pre-service teachers to understand the experience of teaching. This paper examines the development and trialling of variations of a novel affect-based critical moment protocol that enables preservice mathematics teachers to reflect on their teaching performance. The emotions experienced in these moments were examined using self and group reflection, considering the thoughts and actions occurring immediately prior to, or during those moments. The four case studies presented report on trialled variations of this reflection process in a range of programs and delivery modes in four regional Australian universities.