To broaden perspectives presented in undergraduate courses, instructors often invite guest speakers, yet there is limited research on students' perceptions of guest speakers and the potential influence they may have on student learning. In this exploratory study, we describe how senior undergraduate students, in a natural resource management capstone course, perceived guest speakers, who were invited to lecture on environmental socio-scientific issues. Through qualitative content analysis (guided by frame theory) of student interviews, student artifacts, and transcripts of lectures, we determined that, compared to other speakers, 'memorable' speakers (1) told stories, (2) evoked emotion, and (3) either explained theory only after sharing cases studies or intermittently explained theory while sharing a case (rather than beginning with theoretical explanations followed by case studies). Because storytelling was a consistent theme across the 'memorable' speakers, we posit that this instructional strategy can be effective in engaging students. We make recommendations for how instructors can select or prepare guests in interacting with undergraduate students.