Filming may be all but completed for The Dark Knight, but that doesn't mean that there aren't more surprises to come from the production. According to Wigan Today, British actress Sarah Dunn has been cast in a supporting role in Batman's latest adventure.

According to Dunn, "The audition was three months ago and I assumed nothing had come of it because I didn't hear anything. Then I found out a couple of weeks ago. I am just so excited." While Sarah is keeping quiet about the role she has been cast in, the rumor is that she has been cast as Harley Quinn, a beautiful villain and the Joker's sidekick.

Created for the animated Batman and later imported to the comics, Harley Quinn was originally Dr. Harleen Quinzell, a brilliant and ambitious psychologist at Arkahm Asylum and was assigned to try to treat the Joker. The Joker's twisted psychosis proved to be too much for her, and rather than her rehabilitating him, he pulls her into his own insane world. Harley Quinn serves as the Joker's sometimes girlfriend, and perpetually loyal sidekick.

The Dark Knight is set for a July 2008 release, and stars Christian Bale, Heath Ledger, Michael Caine, Morgan Freeman and Gary Oldman. It is also the first Batman film not to include the hero's name in the title.