A direct to video animated movie produced by Warner, featuring the characters and situations of the Kids' WB! series Batman Beyond.
Terry McGinnis, the Batman of the future, and his elderly mentor Bruce Wayne are shocked to realize that the Joker has returned, deadlier than ever. The mystery is, how? As McGinnis points out, he's pretty spry for someone in his 80s. The story includes an extended flashback sequence featuring the classic Batman, Robin, and Batgirl during one of the worst missions of their careers.
It's an exciting, gripping, scary-as-hell story that is well worth viewing...
...if by some miracle you can find the original version.
Originally scheduled to be released in October, Batman Beyond: ROTJ got caught in the backwash of the McCain hearings into violence in entertainment on Capitol Hill. Kids' WB! executives reviewed the videotape and blanched.
Make no mistake: the original story is not for children. It is excessively violent and extreme; not what your average middle-America parent would expect when picking up a Batman video at the Wal-Mart. Perhaps if the level of violence had been toned down a bit, the story could have been left intact. (The wisdom in telling a story unsuitable for children using a popular all-ages cartoon character is debatable. On the one hand, there's creative freedom. On the other hand, there's a justified parental expectation that certain things aren't going to happen in an unrated cartoon with "Kids'!" on the label.)
Instead, massive edits were made after the fact. Going into them into any detail would involve commensurately massive spoilers, which is why I am thoughtfully attaching another hardlink below. Suffice it to say that the story makes less sense now. Most of the action sequences should be just as good as ever, but the character motivations have been blurred irreparably.
If you're so inclined, you may find an unedited screener copy using CuteMX (it was all over the late Scour Exchange). Although it's absolutely Not For Children, the original cut of Batman Beyond: Return of the Joker is a superior, exciting animated story and addition to the Batman mythos.
Batman Beyond: Return of the Joker edit list