In an interview with E!Online, Tom Felton basically says that all the cast is waiting on tinderhooks for someone else in the cast to go mad. Of course, if everyone is waiting for everyone else to go mad, then no one will go mad. But Tom’s got bets on Rupert.
Of course there are other things in the video: Justice to the last movie, Pottermore, What makes Draco Tick (no… not me, incidentally. Heh), who he most wants to do a future movie with, and, of course, the crazies.
Just to let you know, the video starts RIGHT away without prompting, so be careful if your sound is too loud, or muted, and don’t wonder if you’re going crazy and hearing sound where sound should not be heard. You’re not going, as Tom says, off the rails.