When someone is watching a TV show or movie based on a comic book,it's easy to assume each character originated in a comic book, but they would be wrong. In some cases, a character is created specifically for that TV show or movie. Sometimes a creator of a show needs a character that a comic book writer may have not thought of yet, so they create one themselves.
While originating in a comci book, when TV show character becomes a fan favorite, that character is likely to end up in the comics. This whole chain of events happens a lot in Marvel and DC animated shows. Here is are top 10 characters who originally appeared in cinematic/animated adaptations of comics first.
10 Cinderblock
Cinderblock's first appearance was in the 2003 series of the Cartoon Network Teen Titans show in the episode Divide and Conquer. This is the iconic episode where Robin and Cyborg mess up a combo move and stop working together. His first comic appearance was in 2009 in Teen Titans vol 2 #17. He has recently made it back to TV in the episode Staff Meeting of the Teen Titans Go series.
In both the comics and TV, his character is the same: an evil sentient being made of concrete blocks. He is almost always a villain to the teen titans and is usually controlled by Slade or Tara.
9 Livewire
Livewire's first appearance was in the Superman: Animated Series episode Livewire. She worked for a Metropolis radio station as a broadcaster who would regularly bashed Superman. After Superman saved the owner of the Metropolis radio station's wife, he fired Leslie (Livewire) and turned it into a country station.
Since the Superman show, she has since debuted in various DC comics and The Supergirl show on the CW. She has the power of electrokinesis and electromagnetism, but superman and Supergirl learned that her ultimate weakness is water.
8 Mas y Menos
Mas y Menos are 12 year old twins that came from Guatemala and are a part of the titans East Team. Their first appearance was in the 2003 Cartoon Network Teen Titans series where they were first seen in the episode Titans East, Part 1. They have now become a part of DC comics in Teen Titans #38 and have made their appearance in Teen Titans Go.
There powers consist of super speed comparable to the Flash, can only use them when they are psychically touching.
7 Renee Montoya
Renee Montoya is the second person to take over the mantle of The Question. She was created for the Batman Animated Series in the episode P.O.V and has of course made her way into other DC media. While she only had a first name at the time, she was first seen working at the GCPD as the partner to Henry Bullock in the Batman #475 and as the Question 52 #48.
She is also seen in The New Batman Adventures as a detective instead if a police officer. She is also a member of the DC Bombshell figures and comic books.
6 Nora Fries
Nora Fries is the wife of the infamous Mr. Freeze. She first debuted in the Batman the Animated series critically-acclaimed episode Heart of Ice. Sometime in Nora's life she was diagnosed with a terminal illness. Instead of letting his beloved wife die, scientist Dr. Victor Fries cryogenically froze while he searched for a cure.
Nora has transcended her few appearances in the Batman Animated Series to comics, straight to DVD movies, the film Batman and Robin, the batman Arkham video game, and recently, CW's Arrow.
5 Kaldur'ahm
Kaldur'ahm began as the sidekick to Aquaman, dawning the name Aqualad. His first appearance was in the pilot episode of the DC Animated TV show Young Justice. His first appearance in mainstream comics was Brightest Day #4 in 2010. He is now a main charterer in the newest Teen Titan's comic fronted by Damien Wayne and appeared in an episode of Teen Titans Go!
He is the son of Black Manta and an Atlantean Woman named Sha'lain'a. He has the same abilities as a other Atlanteans, including a vulnerability to fire and dehydration.
4 Spyke
Evan Daniels is the nephew of Ororo Munroe, The X-Men known as Storm. He was created for the X-Men Evolution show in the episode Speed and Spyke. Like others in this series, he is just a high-schooler trying to hide his powers in a school full of humans humans.
Spyke has the power to make spikes come out of his body and launch them at potential opponents. Later in the series, he is unable to retract the spikes back into his body. Since then, his body is now mostly an exoskeleton of the spike's material.
3 X-23
Laura Kinney is X-23. Like Spyke, her first appearance was in the X-Men Evolution show in the episode appropriately named X-23. She is a clone of Wolverine and has the same abilities as him, as claws in her feet. She was created by Hydra in a secret facility. While many iterations of the character shoe her with a wild beast like fighting style, in the show, she seemed to be military trained.
X-23 is now a huge character in not only Marvel comics but also the X-Men franchise. she has been the lead multiple comic runs, but has had quite the resurgence since her role in Logan.
2 Batman Beyond
Batman Beyond is the Batman of the future. Batman is too old to hold of the cowl anymore so he finds a good kid to take on the cowl and that kid is Terry McGinnis. Batman Beyond came out in 1999 and Terry's first appearance was in the pilot episode. The show may have ended, but Terry as batman did not. In fact, Batman Beyond has gone on to lead solo comics of his own.
Just like the original Batman, Terry has no powers. Contrary to Bruce though, Terry began as a street fighter and gymnast before being trained.
1 Harley Quinn
Last, but definitely not least, is Harley Quinn. She is probably the most popular comic book character to come from a TV show. Harley's first appearance was in the Batman the Animated series episode Joker's Favor. She not only has been the main character in a wide range of comics, but she has also been in multiple movies, had her own Animated show, and is now the main character in the Birds of Prey (and the Fantabulous Emancipation of One Harley Quinn), which is hitting cinemas in 2020.
She is an extremely important character in TV and comic books. She is shown to be in a very abusive relationship with the Joker and will not leave because she loves him. That said, she has now left the Joker behind and transformed into her own woman, even becoming a hero instead of a villain.