For anyone who hasn't seen this sketch everyone is talking about, it was called "Welcome Back Potter", a sort of parody to the 1970's show "Welcome Back Kotter". In it, they say how Harry was once a student at Hogwarts, but now he has aged and changed, as has Hogwarts (apparently, Hogwarts is now in the hood, and has a subway running through it). It shows him baldish now trying to teach a class while the Welcome Back Kotter theme song plays in the background. I thought it was funny.