9. The Show Marked Miss Martian's First TV Appearance
Introduced early-on in Young Justice's run, Miss Martian was part of the team's original line-up of heroes. Treated as a newbie when it came to the whole superhero thing, J'onn Jonzz's niece quickly ended up becoming one of the show's most efficient heroes (and most popular characters). Ironically, that right there is essentially a microcosm of her journey into the hearts and minds of fans.
As popular as she was, M'gann M'orzz really was a newcomer when Young Justice started. Only introduced into the comics in 2006, the character was basically still starting out when compared to some of the other legendary characters featured on the show like Robin, Speedy and Kid-Flash, but she was still selected to be part of the line-up and, in making her TV debut on it, she was introduced to a whole new audience, becoming something of a household name among comic book fans in the process.
Three seasons in, she's still a core member of the show and has since made her live-action debut on Supergirl - which is, ironically, a show based on the character she was created to replace in the Teen Titans comics.