The Internet is ablaze with rumors that and animated adaptation of The Dark Knight Returns is in the works, possible set to coincide with the release of next summer's juggernaut live-action film The Dark Knight Rises. That would make this the next, next, next, next Direct to Video movie in the pipe for DC Comics (after Green Lantern: Emerald Knight, the also highly anticipated Batman: Year One, and the recently announced loose adaptation of the Tower of Babel arc Justice League: Doom). If accurate, this would be the third Bat-centric animated movie in a row from DC, but after all next year will be the year of the Bat. Besides, this title is well known by a broad audience and I am sure it will sell like hotcakes.
The adaptation of The Dark Knight Returns would not be the first time Frank Miller's classic take on Batman was brought to life onscreen. The Legends of the Dark Knight episode of The New Batman Adventures features a loose adaptation of one scene from The Dark Knight Returns. More recently, in Batman: The Brave and the Bold, the episode Legends of the Dark Mite gave a brief nod to many incarnations of Batman from over the years including the Dark Knight Returns look which was deemed "too psycho." With this leak, perhaps DC will confirm the rumor soon. Otherwise, we will have to wait for the summer Comic Con when next years DtV lineup will be officially unveiled.
EDIT:
Shame on me, I forgot to mention the Dark Knight Returns homage from The Batman (Thanks Kurtis for the reminder). Maybe I was just blocking the whole series out of my head, but the 4th season of the show was actually pretty good. Perhaps the best episode of the season / series, was titled Artifacts. Set in the distant future, Artifacts contained flashbacks to a not so distant future Batman, highly reminiscent of Batman from Frank Miller story. This grittier, older, tank driving Batman was even introduced by Mr. Freeze with the line, "The Dark Knight Returns."
