9. Professor Ian Duncan (John Oliver)
What kind of psychologist do you have to be to end up at Greendale? A terrible, self-serving, alcoholic one, of course. Professor Duncan's open disregard for his job, the school, and many of its students — combined with, not going to lie, his British accent — make his appearances as caustic as they are welcome. His stand-out moment, though, is probably his terrible drunken rap at the Transfer Dance. You know what, I'll just go ahead and quote it: "My name's Ian Duncan and I'm here to say / I'm going to rap to the beat in a rapping way / I've got a real big penis and I drink lots of tea."