Critical events are incidents encountered by teachers in their practice that can potentially provoke questions about the instructional decisions made, gaining an entry to changing and improving teaching practices. Current research often conceptualises critical events as those that occur during instruction, but critical events can also occur before and after instruction, especially in the contexts of lesson study. In this paper, I will unpack the notion of a critical reflection event during the study, plan, and reflect phases of lesson study through three vignettes that happened during a lesson study cycle. This paper examines how lesson study positions teachers to notice critical reflection events that can provoke pedagogical reasoning and action for the purpose of gaining new comprehension.