It’s the 30th anniversary of Batman: The Animated Series and that means another 30th birthday is just around the corner. Harley Quinn appeared in three DC Extended Universe films, leads her own HBO Max comedy series and has her own comic series. Yet the character came not from the pages of DC Comics, but from the background of The Animated Series.

The Harley Quinn of today is much different from when she first premiered. Her role in the DC Universe is no longer just "the Joker's girlfriend." She's also one of the few characters created for an adaptation to become so popular that she was eventually introduced into the canon. When most of her contemporaries are past their 80th anniversaries, Harley is still fresh-faced and new. Yet ironically, this piece of DC's future owes her existence to a relic of TV's past: the daytime soap opera.

RELATED: Harley Quinn May Just Have Secretly Crossed Over With Looney Tunes

Paul Dini has written some of the most beloved Batman stories, but in 1992 he was a freelance writer working on Batman: The Animated Series. He penned the first episode featuring the Joker, and he crafted a story that highlights how excellent the series was. Batman only appears in Season 1, Episode 8 "Joker's Favor" in the final act. The rest of the plot focuses on a poor schlub who had the bad luck to "cuss out" the Joker while driving. The Joker terrorizes the guy, telling him that he's always watching him.

Dini thought about making one of the Joker's henchman a woman, and he used his friend Arleen Sorkin's appearance in a fantasy sequence on the soap opera Days of Our Lives as the model. Sorkin was eventually cast to play the character, though in later years Tara Strong took over the role. But Sorkin's snarky clown on roller skates in the weirdest daytime soap opera has a lot to do with who Harley Quinn is.

Later in the episode, Commissioner Gordon is being honored by some organization for his work... though given what a criminal playground Gotham is, that award must be mostly political. Either way, audiences are treated to a scene of the Joker planning to disrupt the ceremony. The way Harley interacts with him -- disaffected, overly flattering, and slightly terrified -- is a perfect blend of who early Harley was versus who she is today. Sorkin's performance is understated compared to those that followed, but key elements are already in the character, like her humor and her accent.

RELATED: Harley Quinn Just Murdered Gotham's Creepiest Villain Negan-Style

Across the DC Animated Universe and comics that shared its continuity, Harley Quinn subsequently became a massively popular figure with both kids and adults. Filmmaker and outspoken DC fan Kevin Smith somehow convinced his wife Jen Schwalbach to name their daughter Harley Quinn Smith, after the character. Stories like that prove that Harley is easily the most impactful DC Comics character created in the past 30 years.

She also appears to just be getting started. Margot Robbie may be on a break from the character, but Lady Gaga is set to re-imagine Harley in the upcoming film Joker: Folie à Deux. On the TV side, the Harley Quinn animated series recently earned a renewal. While Harley Quinn is only getting even more popular, fans would do good to remember that she started on Batman: The Animated Series -- and owes her start to a soap opera's roller-skating clown.

Harley Quinn streams Thursdays on HBO Max. Batman: The Animated Series is also streaming on HBO Max.