Channel Hop: The current film adaptation has jumped from Disney to 20th Century Fox. A rare example of a film series doing this, as only a few other film series such as Hellboy and Terminator have done it.
Development Hell: Due to rights issues, the fourth film in the series is "on hold indefinitely", and, even if the crisis is resolved, the production won't start before 2014. The franchise isn't officially dead yet, but is certainly on life support.
Enforced Method Acting: To create the right slightly creeped out vibe between the characters, Tilda Swinton (who played the White Witch) would spend time in between shots subtly hitting on Skandar Keynes. Who would have been around 14 at the time.
The four principles were not shown the snowy Narnia soundstage until they were filmed first entering it from the wardrobe, so that their awestruck expressions would be genuine.
In a bit of a meta case, the film was shot in as close to chronological order as possible (as opposed to a normal filming regimen, which is scheduled based on when sets are available and so on), so that the childrens' emotional growth onscreen would be reflected by their physical growth throughout the shoot.
So My Kids Can Watch: Makeup effects artist Howard Berger, whose prior credits include Hostel and Sin City, mentioned in an interview that this would be the first movie he worked on that his kids could watch. He later won an Oscar for his work.
Edmund's actor, Skandar Keynes, is Charles Darwin's great-great-great-grandson.