The five voice actors who play the Royal Flush gang are the same actors who portray the Teen Titans (2003), DC's other hit animated superhero team. The Royal Flush Gang members are also designed after their respected voice actors: Scott Menville (King - Robin), Khary Payton (Ten - Cyborg), Greg Cipes (Jack - Beast Boy), Tara Strong (Queen - Raven), Hynden Walch (Ace - Starfire)
In the shot that Green Lantern goes underwater to find the bomb, in the back left you can see a building with 221 B Baker Street written on it. This is the address of Sherlock Holmes the detective.
The Joker buys his airtime using the alias "Gwynplaine Entertainment." Gwynplaine is the hero of Victor Hugo's novel "The Man Who Laughs," a circus performer who was abducted and mutilated as a child, a permanent grin carved into his face. Batman's creator, Bob Kane, admitted that he and Bill Finger used Gwynplaine as a model when he created the Joker, specifically Conrad Veidt's portrayal of the character in The Man Who Laughs (1928) film adaptation. "The Man Who Laughs" is also the name of a comic serial featuring Batman and the Joker.
The time given by the Joker, is the typical time of an episode minus the commercials.
According to Bruce Timm, the Headmaster of the Royal Flush Gang in the flashback was designed as a cross between Marvel's Professor Charles Xavier, from their X-Men title, and DC's John Lynch, from Gen-13.