The ‘joke’ here is that Dennis is supposed to be aboriginal, hence the anthropologist following him with a recording device. When I drew the strip I was afraid that if I drew him stereotypically–long braid of black hair, no facial hair–I might catch hell from Lakehead University's large aboriginal student body. However, as it turns out, I drew him in such a way that he could look like half a dozen different ethnic groups, and the joke doesn't really present itself without explanation.
Well, aside from the fact that his first name is Dennis, which seems to have been a very popular boys' name for Native people about my age.