This is the first extended look at Batman's corner of the DC universe since the original, legendary Batman: The Animated Series (I'm not counting Batman: Gotham Knight, which existed in its own strange movie-influenced continuity), and so at first it's a bit weird to see Batman and the Joker do battle without hearing Kevin Conroy and Mark Hamill. That said, as much as Conroy is the definitive Batman, Bruce Greenwood is maybe the best alternative take I've yet heard, which may have something to do with the fact that he sounds an awful lot like Kevin Conroy. Still, he brings a fatherly pain to his performance that really makes the role his own. Here's hoping this isn't the last time we get to hear Greenwood play the Dark Knight.
John DiMaggio, on the other hand, offers a take on the Joker that is very, very different from the iconic Mark Hamill version. I was a little concerned that the voice of Bender playing the Joker would prove distracting, but his bass-heavy interpretation suited this more brutally murderous incarnation of the Joker. Jensen Ackles and Jason Isaacs were both solid as Jason Todd and Ra's al Ghul, but the standout here was, unsurprisingly, Neil Patrick Harris as Nightwing. It probably helped that he got every joke in the movie, but he turned a bunch of semi-humorous lines into laugh-out-loud moments. A full-on Greenwood/Harris team-up movie is something I would definitely love to see.
So, it's Captain Pike and Dr. Horrible battling Bender and Lucius Malfoy for the soul of Dean Winchester. AWESOME.