In many contexts, implementing CLIL is top-down, in which the policy is imposed on teachers to transform monolingual content classes into CLIL classrooms. This implementation brings several challenges to content teachers, who were previously trained as content specialists only. This study attempted to explore the lived experiences of these CLIL teachers, who were obliged to implement CLIL because of the school policy. The study utilised trajectories of learning as a theoretical framework and employed a narrative case study to interview five in-service CLIL teachers. The findings revealed that the teachers entered the CLIL community by accident; they were assigned to teach CLIL by the school directors simply after visiting a CLIL school. Even though their trajectory was accidental, these teachers moved to an insider and inbound trajectory through constant practice, networking, and extensive professional development. This paper argues that converting a monolingual content classroom into a CLIL classroom is more than changing a language of instruction; instead, it takes one's identity.