Since concept cartoons give an important opportunity for students to achieve informal physics learning, the current research focused on pre-service teachers' initial impressions of the concept cartoons in the school corridors and informal physics learning. The aim of the research was to determine pre-service teachers' initial impressions of the concept cartoons in the school corridors and informal physics learning via the concept cartoons. After a 14-week intervention, a questionnaire with seven open-ended questions was administered to 542 pre-service teachers from primary, mathematics and science teacher education programmes. Their responses to the questionnaire were exposed to qualitative content analysis via two categories (advanced and poor impression). The results showed that pre-service teachers generally refered to advanced impressions of the concept cartoons. In light of the results, it can be deduced that the concept cartoons have enhanced their initial impressions of informal physics/ science learning via the concept cartoons. The current research recommends that pre-service teachers should be encouraged to produce their own concept cartoons on the topic(s) they found difficult.