The use of virtual teachers (VTs) in environmental education is an important but little-studied issue. The advantage of VTs over robot teachers is that they have more freedom in designing their appearance and can change it immediately. Therefore, this paper hypothesizes that 'VTs with animal ears are better suited to teach environmental issues related to animals'. To verify this hypothesis, I conducted a two-factor and two-level experiment. The first factor was the appearance of the VT, which I defined as cat ears level and human level. The second factor was the lesson theme, I defined the invasive species problem level and the acid rain problem level. The measure of lesson effectiveness was a questionnaire answered by the participants. Results showed that only when the lesson topic was 'Invasive Alien Species Issue', participants indicated that VTs with cat ears were more knowledgeable and more trustworthy on the lesson topic than VTs without cat ears. When asked if VTs were interested in the lesson theme, the results were more clear: VTs with nekomimi felt that they were more interested in the theme than VTs without nekomimi only if the theme was an invasive species issue.