- Acting for Two: Freddy Highmore played both Jared and his identical twin Simon in the film version. Their personalities are complete opposites.
- Actor Allusion: Nick Nolte, who plays Mulgarath in human form, had previously starred in another movie with a creature that turns big and green when angry.
- Cast Incest: Freddie Highmore and Sarah Bolger◊ dated, despite playing brother and sister.
- Fake American:
- British Freddie Highmore as both Simon and Jared.
- Irish Sarah Bolger as Mallory.
- Joan Plowright as Lucinda is an odd case. Lucy as a child speaks with an American accent, but has an English one as an old woman. She also reverts back to her American accent when she's restored to her youth.
- Playing Their Own Twin: Freddie Highmore plays the twin brothers Simon and Jared. He gives them their own distinct looks, personalities and voices.
- Separated-at-Birth Casting: A lot of viewers thought this was the case with Simon and Jared, as widely documented.
- The Wiki Rule: The Spiderwick Wiki.
Trivia / The Spiderwick Chronicles