DC Universe's new Harley Quinn series features cameos by a large number of DC Comics characters. Many of these are Batman villains and allies, as befits the Gotham City setting, but the show's trailers have revealed that the Clown Princess of Crime will be confronting heroes and villains from all corners of the DC Universe soon enough.
The Harley Quinn series premiere, "Til Death Do Us Part", sets the stage for the series at large and introduces the main players. We learn how Dr. Harleen Quinzel was once a brilliant psychiatrist until she developed a serious case of Stockholm Syndrome for one of her patients - the psychotic maniac known as The Joker. However, the Clown Prince of Crime's spell over his sidekick was broken after she spent a year locked up in Arkham Asylum waiting for him to help her escape. With the help of another of her former patients, the plant manipulating Poison Ivy, Harley escapes both the asylum and her abusive relationship, deciding to prove that she can beat her ex-boyfriend at his own game by becoming the queen of Gotham City's underworld and earning a spot in the Legion of Doom.
The Harley Quinn series is a brilliant send-up of traditional superhero cartoons, offering a look at the realities of supervillainy comparable to those episodes of The Venture Bros. focused upon the Guild of Calamitous Intent. Fans of DC Comics, however, will enjoy Harley Quinn's twister take on their favorite characters and the wide variety of cameos in every episode. Here is a run down of all the DC Comics characters to be seen in Harley Quinn's premiere episode.
Harley Quinn
Voiced by Kaley Cuoco (Penny on The Big Bang Theory), the series' take on Harley Quinn comes directly from her New 52 comics' series. She wears Harley's famous roller derby costume, but she sports the partly pink and blue hair of Harley's costume from the live-action Suicide Squad movie. The first episode details how Harley decides to rid herself of her ex-boyfriend and establish herself as a supervillain on her own terms.
The Joker
Voiced by Alan Tudyk (Mr. Nobody on DC Universe's Doom Patrol), Harley Quinn's take on The Joker is cut in the classic mold of his counterpart from Batman: The Animated Series. Comic and horrifying in equal measure, he doesn't take Harley's attempts at independence seriously at first. He does, however, pour on the charm to keep her under his thumb... right up until she blows up his hideout.
Batman
The true object of affection in Joker's life (though Harley is slow in realizing it), Harley Quinn's take on Batman is totally humorless and utterly unflappable. This makes him a perfect foil for The Joker and for Harley, as she starts trying to take over The Joker's territory. He is voiced by Diedrich Bader, who previously played the Dark Knight Detective in the Batman: The Brave and the Bold cartoon.
Commissioner Gordon
Over-caffeinated and under-appreciated, Gotham City's Police Commissioner Jim Gordon is a good cop frustrated by the incompetence of his department and the insanity of the criminals he has to deal with on a daily basis. This leaves him perpetually on-edge and isolated; an issue that has left him desperate for companionship, leading to countless awkward invitations to hang out which Batman pointedly ignores. He is voiced by Chris Meloni, who previously played Detective Elliot Stabler in Law and Order: SVU.
Calendar Man
Originally a gimmick villain who committed crimes based around specific dates and holidays, Julian Day was later reworked into a serial killer who based his murders around notable anniversaries and the passage of time. Harley Quinn's version of Calendar Man is decidedly less serious, being an agreeable fellow who can count to the day just how long Harley has been locked up in Arkham Asylum without The Joker trying to rescue her. Despite this, he is somehow unable to remember his anniversary, much to his wife's annoyance. He is also voiced by Alan Tudyk.
The Riddler
Mocked by an abusive father who called him stupid, Edward Nygma grew up determined to prove to the world that he was smarter than everyone else. This led him to become a costumed criminal known as The Riddler, who tested the puzzle-solving abilities of superheroes everywhere, even as he tested the patience of his fellow villains. Still, he's a good guy to have on your team on trivia night at Arkham Asylum and he does take a hand in helping Harley win free of Joker's influence. He is voiced by Jim Rash, best known for playing Dean Craig Pelton in Community.
Killer Croc
Born with a disease that gave him the scaly skin of a reptile, Waylon Jones would later be mutated into a true hybrid of man and crocodile. Known as Killer Croc, he possess a brilliant criminal mind in the comics but is usually portrayed as dumb muscle in most of his animated appearances. It is unclear how smart or strong Harley Quinn's version of Killer Croc is, though he is dumb enough to tell Harley that Joker is never going to rescue her from Arkham Asylum and weak enough to get thrown around by Harley once she is enraged. He is voiced by Matt Oberg, who played Buddy Calhoun on Veep.
Poison Ivy
Even before she was turned into a half-plant hybrid by her mad college professor, Pamela Isley preferred plants to people. Today, Poison Ivy still wants to destroy the world as we know it, but she was convinced that not all people are horrible by a young psychiatrist named Harleen Quinzel. It is for this reason that Ivy takes Harley Quinn on as a project and starts trying to help bring back something of the woman who once helped her, becoming her best friend in the process. She is voiced by Lake Bell, who also voices Katrina Peanutbutter on BoJack Horseman.
Man-Bat
A brilliant zoologist who suffered from hearing impairment, Dr. Kirk Langstrom created a serum he hoped would give him a bat's sonar sense. Instead, the formula transformed him into a creature that was half-man and half-bat; a Man-Bat! Over the years Man-Bat has been both a berserk monster and an ally of Batman. Harley Quinn's take on the character is civilized enough to wait in the lunch line at Arkham Asylum, but he is apparently not a fan of the cooking.
KGBeast
Master of several martial arts and cybernetically enhanced by the finest technology the Soviet Union could afford, Anatoli Knyazev was the greatest assassin in KGB history. Known as "The Beast" to his handlers, he was known by a different name in the United States; KGBeast. Knyazev can be briefly seen in the background of one scene, along with Killer Croc and Man-Bat, as they (and everyone else in the lunch room of Arkham Asyluym) try to tell Harley Quinn one last time that The Joker is not coming to rescue her, despite her belief to the contrary.