The Harry Potter film series had some of the best actors in Britain -including David Tennant just before he was cast as The Doctor. While it's always fun to imagine actors playing their most famous roles in their other films, it's particularly easy with David Tennant, since the Tenth Doctor once wiped his memory so he thought he was human just to hide out from a particularly evil family of aliens.
This mashup with Harry Potter is perfect for those who love imagining that Bartleby Couch Jr. is just a strange and confused Doctor in hiding.