As soon as it premiered on the DC Universe streaming service, Harley Quinn proved to be a breath of fresh air. Separate from the DCEU and even the DCAU, the adult animated series reinvented many of the most memorable characters from DC Comics. Often, it was for the better.

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Harley herself, as well as Poison Ivy, Joker, and the members of Harley's crew all stood out as great characters. However, the show wouldn't be near as fun without the supporting heroes and villains. These are the side characters who get a lot of screen time, some of whom are much better than others.

Lex Luthor

Lex Luthor appears in Harley Quinn animated series.

It makes perfect sense that the talented Giancarlo Esposito voices Lex Luthor. There's something about his calm demeanor that works perfectly for Luthor. He shows up in a handful of episodes as the leader of the Legion of Doom who Harley constantly tries to impress.

Luthor manages to nearly steal the scenes he's in because of how he carries himself. There's a coolness factor to this guy that makes you understand why other villains would want to follow him. He's also kind of a main antagonist for most of the first season but disappears afterward.

Superman

Wonder Woman, Superman, and Green Lantern in Harley Quinn

When fans first thought about the Harley Quinn animated series, their minds might not have gone to characters from outside of Batman lore. Yet some other top superheroes appeared, including the other two members of the DC Trinity, Wonder Woman and Superman.

While Wonder Woman (Vanessa Marshall) was good, Superman (James Wolk) is a treat. Whenever he opens his mouth, he's bound to say something corny. It's a fun and interesting take because it plays right into the idea that Superman is unstoppable but he's kind of uncool at times.

Catwoman

Catwoman in DC Universe's Harley Quinn Trapped

First appearing in season two's "Trapped," Catwoman (Sanaa Lathan) gets off to an intriguing start. She has a past with Ivy, who gets flustered around her because of how cool she is. Of course, Catwoman betrays Harley and Ivy in that episode but she also helps Ivy realize things about her life.

Catwoman shows up again near the end of the season in "Bachelorette," joining Harley, Nora Fries, and Jennifer as part of Ivy's wedding party. Once again, she's fun to have around in this episode. It would've been nice to have her around a bit more, though.

Batgirl

Barbara Gordon talks to her dad

One of the highlights of the second season was the episode, "Riddle U." It takes the core characters to college where they meet Barbara Gordon (Briana Cuoco). She's fun at first but she only gets better when you find out that she's Batgirl and she shows up several times after.

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Batgirl makes for a good inclusion because it keeps the focus on the females of the story. Barbara's relationship with her father provides some enjoyable moments, as do her appearances at Batgirl in a handful of heroic moments throughout the season.

The Riddler

Harley Quinn Show The Riddler

The Riddler (Jim Rash) is actually one of the most frequently appearing characters in the series. He's in the very first episode as part of the plot devised by Ivy to get Harley to understand how Joker really feels about her. From there on, he's in some major storylines.

That includes being part of the Injustice League, Riddle U, and getting captured by and eventually recruited by Sy Borgman for his evil plan. The fact that he shows up so often, has several plots, and the way that Rash portrays the character are all the reasons why he comes across as quite interesting.

Mr. Freeze

Mr Freeze sacrifices himself in the Harley Quinn series

Although Mr. Freeze (Alfred Molina) doesn't show up anywhere near as often as someone like The Riddle, he makes an outstanding impact. He's first really seen as a member of the Injustice League but he's the one who really manages to stand up to Harley and her crew.

In fact, he captures them in "Thawing Hearts" and explains the troubles that he's had in his attempts to save his wife from a deadly illness. The episode was one of the best of the series due to that story and it helped turn Mr. Freeze into an interesting and sympathetic character who fans wish was around longer.

Batman

Harley Quinn Animated Series Batman

For a series that is based on Batman characters, it's interesting how little of Batman (Deidrich Bader) is actually in it. He plays a larger role in the first season, often arriving in time to either save the day or at least thwart Harley's plans. Season two features a lot less of him after Gotham is destroyed.

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Whenever Batman is around, he's a highlight. He works kind of as a straight man to those cracking jokes around him, even being unintentionally funny himself. His arc is also rather interesting, as he must come to accept that he needs help at times, from Gordon or even Harley and Joker.

Bane

DC's Harley Quinn Show Bane With Umbrella Drink

In terms of purely being pivotal to the overall story or having a character arc, Bane (James Adomian) wouldn't rank all that high. However, he manages to steal every scene that he's in. This take on the villain utilizes a comical version of the voice used by Tom Hardy in The Dark Knight Rises.

He's also the pushover among the rest of the Legion of Doom/Injustice League, despite being massive in size. That concept combined with the voice made Bane the ultimate source of comedy. He's also used just the right amount, giving fans just enough without going into overkill mode.

Commissioner James Gordon

Commissioner Gordon in Harley Quinn

Nobody expected this version of Commissioner James Gordon (Christopher Meloni) to be so wild, no matter how many changes this series made to characters. For starters, it's always hilarious to see Gordon interact with Batman, as he tries desperately to become friends with him or gain his acceptance.

Just look at how excited he was to use one of Batman's vehicles. Gordon needs to not only be a hero but also to have companionship. He tries to get close to Barbara after a while but the true high point for him was in "You're a Damn Good Cop, Jim Gordon," when he befriends Clayface's hand. Gordon gets some of the best storylines of the series.

Kite Man

Kite Man

Hell yeah! When Kite Man (Matt Oberg) makes his first appearance, he's treated like a joke by everyone around him. They view him as a loser who has a costume and name that don't put fear into the hearts of anyone. He tries hitting on Ivy and comes across as lame.

However, he actually grows into one of the most beloved characters. His relationship with Ivy is sweet as he's always trying his hardest to prove that he deserves her. He clearly loves her and is still a constant source of comedy. You also both feel sad for him and are happy when he realizes that Ivy will never truly love him and he can move on.

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