They grow up so fast, they say. No, not in regards to parents and their children, but to superheroes and their super sidekicks. One second, those crazy kids are cracking snappy quips by their big honcho's side. The next second, they end up leaving the nest to fly solo or, in some cases, join a league of their own. On some occasions, that league is quite literally the Justice League.
In the DC Universe, the Justice League is the most prestigious superhero group any hero could belong to. Obviously, not every hero and especially not every former or current sidekick is allowed to slip through the crack. But in some cases, that former sidekick wound up earning their stripes enough as a solo act to pass the recruitment process.
10 Wonder Girl Becomes Her Own Woman
Donna Troy was originally conceived simply as a sidekick made to literally be a Wonder Woman clone, created after Diana Prince looked into the eyes of a magic mirror. However, in due time, Donna was able to make an impact in the DC Universe beyond just being a sidekick.
She made a name for herself on her own merits as one of the founding members of the Teen Titans. Even further, she once briefly took on the Wonder Woman mantle. All of her deeds demanded the attention of the Justice League, leading to the original Wonder Woman asking Donna to join the team.
9 Dick Grayson Leads A Version Of JLA, Before Joining Again As Batman
Ever since he left his adopted father's side to become Nightwing, Dick Grayson has been portrayed either as the leader of the Titans or an entirely solo act. Though, there are a couple of instances where he became a member of the Justice League.
The first being Joe Kelly and Doug Mahnke's JLA #69, where Batman assembles a new Justice League to investigate the disappearance of original JLA members, introducing Nightwing as "the only one I could have picked to lead you." Years later for James Robinson, Mark Bagley, Rob Hunter, Marlo Alquiza, and Walden Wong's Justice League of America #41, after Bruce Wayne's apparent death, Dick Grayson took over his cowl and his spot in the League.
8 A Superpowered Damian Wayne Enters The Fray
Speaking of Dick Grayson, Dick's successor to the Robin mantle, Damian Wayne, promptly demanded to be added to the Justice League line-up upon being present for Dick's induction hearing into the group at some point during Batman: Reborn. His demand was promptly ignored, but his wish was granted some years later in Batman & Robin #40 by Peter Tomasi and Patrick Gleason.
At this point, the 10-year old boy had acquired superpowers, which influenced the League's decision to call upon him. Although, Damian's alliance with the League isn't a permanent one and lasts a short amount of time.
7 Red Robin Joins The Justice League Task Force
Speaking of Bruce Wayne's apparent death, the reason why it was so apparent is that rather than actually dying, he was sent back in time. The Justice League called on Red Robin to join an expedition to bring the original Batman back to the present. For those wondering who Red Robin is, he's Tim Drake all grown up.
After Tim saved his old man and the two teamed up once more to defeat the Council of Spiders, he went on to join the Justice League Task Force, a JLA covert strike operation mostly comprised of members of Justice League Europe and Justice League International.
6 Mary Marvel Marvels As A Super Buddy
For those unaware, Billy Batson has an older twin sister named Mary who, just like the former Captain Marvel, has adopted the powers of Shazam. Over the years, she has been closely linked to the Justice League, appearing in a few different iterations of the team.
One of them including an early 2000s version called the Super Buddies featured in a mini-series called Formerly Known As The Justice League. She also featured a member of JLA during the Justice League Beyond digital comic series, depicting the JLA in the future of Batman Beyond. Though, oddly enough, this is a future where Mary Marvel somehow shares a body with Shazam and Black Adam. Long story.
5 Supergirl Finds Herself In The DCAU JLA
Transitioning from the comic book world and over into the DC Animated Universe, Supergirl gradually went from being Superman's sidekick cousin introduced in Superman: The Animated Series, making space cameos here and there in Justice League, to being a full-blown member of the League starting in Justice League Unlimited.
In the series premiere episode "Initiation," Supergirl is one of many recruited heroes assembled as part of the JLA's expansion plan, where she was able to earn her stripes on her first mission in Chong-Mai.
4 Aquawoman Spent Her Childhood At The Hall Of Justice
With her parents being two Justice League members in the form of Mera and Aquaman, Andy Curry already was more than familiar with the Justice League, often visiting the Hall of Justice with her parents during her formative years. She started her own superhero duties young as Aqualass, playing second fiddle to not only her father but her brother, the former Aqualad, Jackson Hyde.
She never liked the name Aqualass, though, and when she grew into a proper adult, she asserted a name change in Aquawoman. Also in adulthood, they joined forces with the next generation of heroes to form a new Justice League.
3 Roy Harper Becomes The Hero He Was Born To Be
Roy Harper has always had a complicated history with the Arrow family and its namesake. Green Arrow first brought Harper in as his ward, Speedy, but upon discovering his sidekick suffered an intense heroin addiction, he angrily kicked Roy out of his home.
Speedy went on to conquer his addiction, rebranding as Arsenal, and even reconcile with Oliver Queen, though remaining solo. After committing to some impressive work as a member of the Outsiders, Hal Jordan and Wally West asked Roy to join the Justice League. Not only did Harper accept the position, but he also rebranded once more as Red Arrow to make peace with his legacy.
2 Wally West Replaces Barry Allen In The JLA
Wally West worked hard to climb the ladder of prominence atop the DC Universe. Similar to Dick Grayson, he was introduced as a sidekick to The Flash, appropriately named Kid Flash, before eventually growing up to don his mentor's costume as the third Flash.
In between that time, West earned a spot on the Teen Titans as the Kid Flash, but when his idol sacrificed himself during the Crisis on Infinite Earths storyline, Wally was forced to take his place as the new Flash. The perks of becoming The Fastest Man Alive included replacing Barry Allen as a member of the Justice League.
1 Harley Quinn Beats Brainiac And Earns Her Place In JLA
After years of fighting off members of the League, Batman in particular, alongside The Joker, Harley Quinn might be the most unlikely member to join, but it's happened on at least two occasions. One is on the cover of Superman #19 by Brian Michael Bendis. In artwork designed by Ivan Reis, Superman is surrounded by members of the League at the Hall of Justice, with Quinn planting a firm seat of her own at the table.
How she joined the League isn't explained, but it could be a continuation of the Injustice 2 video game, where if the player uses Harley Quinn to defeat Brainiac at the end of the Multiverse Ladder Story Mode, it's revealed Quinn is offered a spot in the League by Batman himself, which she seemingly accepts.