According to an interview with Neil Gaiman, the original computers used to do all of the CG were named after the Beatles (John, Paul, Ringo, George). Later a fifth computer was required, so it was named Yoko. Soon after the fifth computer was introduced, the network crashed and could not be restored properly ("the computers refused to talk to each other"). A new server and computers were purchased and named after The Ramones (Joey, Jonny, DeeDee and Tommy). Gaiman said "I wish I knew more about the history of The Ramones; the computers performed brilliantly, vibrantly and died an untimely - and early - death"

During the circus montage at the beginning of the film, there is a brief shot of a hand balancing and twirling a set of four crystal balls. This art is called Contact Juggling, created by performance artist Michael Moschen and originally debuted in the Jim Henson film Labyrinth (1986), which in part inspired this film.

According to Neil Gaiman, this film was made as a straight-to-DVD film; but this film finally got a limited theatrical release in the United States.

Total number of digital fish in the film: 42.

When Helena reaches for the copy of "The Complete History of Everything" in the library, the book directly beside it is entitled "Muppets in Space," using the font from Farscape (1999). "Farscape" is another Jim Henson Company production set in space. This joke is often mistaken for Muppets from Space (1999), the 1999 film.

Josefine Cronholm's version of Burt Bacharach's classic song "Close to You", performed in the film during the scene where Helena is dressed by mechanical handmaidens, was inspired by composer Wayne Horvitz's 1997 cover version of the song featured in the tribute album "Great Jewish Music: Burt Bacharach" (sung by Julie Wolf and Robin Holcomb).

There were 70 masks within the film.

The designs were done by Dave McKean; Neil Gaiman and McKean also collaborated on the illustrated film script.

The MirrorMask title is shown on the record that is playing when Helena and Valentine enter Mrs. Bagwell's apartment.

Was nominated for the William Shatner Golden Groundhog Award for Best Underground Movie. The other nominated films were Green Street Hooligans (2005), Nine Lives (2005), Up for Grabs (2004) and Opie Gets Laid (2005).

Highest number of setups in a day: 48 Number of days on location: 10 Number of days in the studio: 20 Total number of effect shots: 1139 Number of animation days per shot: 3.5

Number of animators on the film: 15 Number of animation days per shot

Total number of scenes in the script: 135 Total number of pages in script: 107 3/4

Dave McKean: the motion capture performer for the porcupine wearing braces. His character also appears waving during the end credits.