•Mark Hamill and Kevin Conroy will reprise their frequent roles of The Joker and Batman, respectively. You may remember the sounds of their pipes from Arkham Asylum, as well as any other animated Batman project from the past 15 years.
•Former Firefly stars Gina Torres and Adam Baldwin will voice Wonder Woman and Superman, respectively. Though you probably didn't need that "respectively" bit, due to your understanding of gender.
•James Marsters will voice balding mastermind Lex Luthor. After playing Spike in Buffy, Brainiac in Smallville, Captain John in Torchwood and Piccolo in the recent Dragon Ball movie, this should be a nice notch in his nerd-fame belt.
•Wonder Woman's adversary, Circe, will be voiced by Michelle Forbes, who provided the voice for Dr. Mossman in Half-Life 2. She's also been in every sci-fi show ever made. All of them. Seriously.