This chapter focuses on learners’ alternative conceptions. The importance of the inclusion of this topic in the Methods of Teaching Computer Science (MTCS) course stems from the fact that prospective teachers in general, and prospective computer science teachers in particular, face difficulties in comprehending the notion of alternative conceptions. The inclusion of this topic in the MTCS course enables to highlight the message that a learning opportunity exists in each pupils’ mistake (or misunderstanding). The chapter presents several pedagogical tools for exposing learners’ alternative conceptions and proposes several activities to be facilitated in the MTCS course that focus on the identification of learners’ alternative conceptions.