Trivia: In a shot of Zeus sitting on the throne, Emma Thompson, in costume as Nanny McPhee, is actually hiding behind the throne - they were filming next to each other. The story was related during an interview - she sneaked on set during a break, sat on Liam Neeson's lap and said "I think you've been a very naughty boy". He suggested she stay when filming resumed, as the shot wasn't going to be on him anyway, but she didn't want to throw off Ralph Fiennes, so hid behind the throne to get out of the way, and a shot of it with her hidden behind, unseen, is in the movie.
Trivia: Bubo the owl from the original Clash of the Titans makes a brief appearance when the soldiers of Argos are putting together their supplies and arms for the trip to meet the witches. Perseus picks up a staff out of a chest of assorted weapons with a mechanical owl atop of it and asks the Captain "whats this?" the Captain replies harshly "Put it back!"