Over the course of its run there have been several major DC Comics storylines that helped influence the spirit and action behind the Supergirl television show. Already in its fifth season, there has been enough material from DC Comics history for the super-heroine drama to adapt and help the show discover its own original voice in the Arrowverse. There have been many familiar faces, including allies and super-villains, who have made their way onto the CW show.
Though she may be Superman's cousin, Supergirl has been able to demonstrate her own strengths and identity. When she was 12 years old, Kara Zor-El was forced to leave her doomed planet of Krypton on a spaceship. Her true destiny was to take care of her baby cousin, Kal-El, when they landed on Earth. Because her cousin arrived first, Kara discovered he had already been raised by another family and learned how to control his extraordinary powers without her. In her own coming-of-age journey, Kara (Melissa Benoist) grew up in a different lifestyle with her foster sister, Alex Danvers (Chyler Leigh), and learned how to be her own hero.
10 10. Crisis On Infinite Earths
The epic crossover event, Crisis on Infinite Earths, was finally adapted into a five-part miniseries event, starting from Supergirl and ending with Legends of Tomorrow.
In the race to save the Multiverse from the Anti-Monitor, the Flash and Supergirl sacrificed themselves in order to save the day. Though there are still two episodes left, there have been a few easter eggs planted throughout. The popular cover of Superman crying and holding his dead cousin in his arms has been changed. Now it's Supergirl holding onto her cousin as he dies in her arms.
9 9. Reign
Making her first appearance during the New 52 era, Reign, an experiment created by Kryptonian scientists, was played by Odette Annable in the third season of Supergirl.
In the comics, Superman's cousin would end up tacking the WorldKiller in the busy streets of New York City. Supergirl was outnumbered, just like she was on the show, as she faced off against Reign and three other violent Worldkillers. Samantha Arias (Annable) had to be the one who could defeat the evil Reign because only a WorldKiller can actually defeat another Worldkiller.
8 8. For The Man Who Has Everything
Superman Annual #11, "For the Man Who Has Everything" introduced the Black Mercy, an extraterrestrial plant-like organism that attached itself to its victims. Like a parasite, the Black Mercy injects hallucinogens into its victims while incapacitated. Superman was unable to wake up from his surreal dream because he was living happily on Krypton.
During the first season of Supergirl, Kara fell victim to the same Black Mercy and imagined a life where Krypton was never destroyed. Luckily, Kara was finally able to wake up from this hallucinogenic world.
7 7. Red Son
In the alternate reality of Superman: Red Son, the Man of Steel's space pod landed somewhere between the USA and the USSR. Because he never swore allegiance to America, Superman fought for Stalin and socialism.
The fourth season of Supergirl took this concept and ran with the idea, setting up a clone of the Girl of Steel. Created by black kryptonite, Supergirl's clone ends up in Siberia. Trained in secret by the Soviet military, the Supergirl clone is adopted by Lex Luthor (Jon Cryer), who then names her as his Red Daughter.
6 6. World's Finest
During the '90s, the World's Finest crossover featured Batman and Superman teaming up together, instead of fighting each other to the death, like in Frank Miller's version.
When Superman discovers Lex Luthor is committing crimes over in Gotham, Clark Kent decides to report on the poverty rate in the city and help the Dark Knight. After Perry White shares a newspaper that called out the two heroes, the two shake hands before separating.
In the Elseworlds crossover, Batwoman and Supergirl mentioned the two are the World's Finest, shook hands, and finally departed.
5 5. Superman #199
In Superman #199, the Man of Steel found himself in a publicized race against The Flash to find out who was the fastest. Due to the bets being placed, the two superheroes felt the money would be better off spent to benefit the United Nations.
During the first season of Supergirl, The Flash (Grant Gustin) ran so fast, that he accidentally ended up on Kara's planet. In order to get back to his earth, Supergirl and the Flash would have to race each other. Supergirl would then use her speed to help the scarlet speedster open up a portal.
4 4. The Curse of Lena Thorul
In Superman’s Girlfriend Lois Lane #23, the Daily Planet reporter was covering a story about witchcraft. Lois Lane's investigation led to Lena Thorul and an even bigger revelation. Superman discovered Thorul also spelled out Luthor. Lex Luthor begged Superman and Lois to kill the story because he did not the entire world to know Lena was actually his sister.
Making her appearance in the second season of Supergirl, Lena (Katie McGrath) struggled to make a good name for herself because her brother, Lex, had committed horrible crimes against Superman.
3 3. Agent Liberty
Created by Dan Jurgens, Benjamin Lockwood was once a former CIA agent, who had grown disenchanted with the government. Disgusted with the government, Lockwood then joined the paramilitary group known as the Sons of Liberty. As Agent Liberty, Lockwood believed the government was meant to be overturned.
During the fourth season, the formation of the Sons of Liberty came about as a human/supremacist group who felt illegal aliens were destroying America. Sam Witwer played the role of Ben Lockwood, who would eventually become the hateful leader of the Children of Liberty.
2 2. Valor
In his origin story in Superboy #89, Halk Kar, aka Mon-El, crashed landed on Earth in his own spaceship. After being discovered by Superman, Halk Kar suffered from amnesia and couldn't remember his homeworld was actually Daxam.
During the first finale of Supergirl, Mon-El (Chris Wood) arrived on Earth in an escape world, due to the collapse of Daxam. In Valor, Mon-el had trouble trusting Supergirl because, at the time, she was Lex Luthor's lover. In both the TV show and in the New 52, Mon-El is the field leader of the Legion of Super-Heroes.
1 1. Legion of Super-Heroes
The Legion of Super-Heroes is a group of time travelers inspired by the legendary heroics of Superman. They traveled back in time to recruit the teenage version of their iconic hero, Superboy.
During the third season, Mon-El returns from the future and introduces Supergirl to the Legion. Saturn Girl (Amy Jackson) and Brainiac-5 (Jesse Rath), aka Brainy, were inspired to form the Legion because of the many heroic deeds of Supergirl. The Legion has traveled back in time in order to help Supergirl defeat Reign and prevent a major catastrophe from taking place.