It's been officially announced that the Joker will be an exclusive playable character for the up coming Batman: Arkham Asylum...

Official Press Release:
Eidos Interactive and Warner Bros. Interactive Entertainment announce that The Joker will be an exclusive playable character in Batman: Arkham Asylum for the PlayStation®3 computer entertainment system. The character will be made available upon release as a free down loadable character through PlayStation®Network for the PLAYSTATION 3 and can be played in Challenge Maps from the game. Fans can get additional information in the June issue of PlayStation: The Official Magazine.

In Batman: Arkham Asylum, DC Comics’ DARK KNIGHT takes on his greatest challenge yet when he becomes trapped with all of his most dangerous villains inside the insane asylum of GOTHAM CITY - ARKHAM ASYLUM! Batman: Arkham Asylum exposes players to a unique, dark and atmospheric adventure that takes them to the depths of Arkham Asylum – Gotham’s psychiatric hospital for the criminally insane. Gamers will move in the shadows, instigate fear amongst their enemies and confront The Joker and Gotham City’s most notorious villains who have taken over the asylum. Using a wide range of Batman’s gadgets and abilities, players will become the invisible predator and attempt to foil The Joker’s demented scheme. Batman: Arkham Asylum features an original story penned exclusively for the game by famous Batman author and five-time Emmy award winner, Paul Dini, whose credits include Lost season one and Batman: The Animated Series.

Published in North America by Eidos, Inc. and Warner Bros. Interactive Entertainment, Batman: Arkham Asylum will also be available June 2009 on the Xbox 360 and PC.