Harley Quinn's Nickname For The Joker Is Complicated Thanks To Conflicting Origins
When thinking about the most recognizable superhero characters in American pop culture, figures like Superman, Batman, and even Spider-Man have decades of history to pull from. Superheroes may be in their Hollywood golden era, but they're also seminal staples, enjoyed and passed down between generations. And then there's Harley Quinn, one of the most easily recognizable figures in the canon of DC Comics heroes and villains, who didn't appear until 1992. Created by Paul Dini and Bruce Timm for "Batman: The Animated Series" as a henchwoman for the Joker, Harley quickly became a fan-favorite, especially with the legions of women who loved all things Batman. There were plenty of women in Batman's rogues gallery like Poison Ivy or Catwoman who had been around since the 1960s and 1940s, respectively, but Harley Quinn was different.
Being affiliated with the Joker certainly helped her star power, but it was the combination of her manic cheerfulness and penchant for ultraviolence that made her a star, and she's since gotten her own live-action film starring Margot Robbie with "Birds of Prey," and the hugely popular eponymous animated series on Max. Since Harley is a relatively new character compared to the rest of the denizens of Gotham, her story, characterization, and look have evolved many times over the last 30 years. This also means that there's a little bit of confusion regarding the origins of some of her most memorable attributes — like why the heck she calls the Joker "puddin'" as a term of endearment.
Harley loves her puddin'
Harley has a handful of nicknames for the Joker, with "Mista J" and "puddin'" the most prominent. Most have chalked up the names as remnants of her frequently put upon singsongy, working-class New York accent, but the puddin' name has been canonized over the years. They honestly could have gone without explaining it as it's not uncommon for someone to call their paramour "sweetheart," "pumpkin," or even "snookums," but this is a character in a world created by comic books ... of course, there's going to be an eventual explanation.
In "Batman: White Knight: Harley Quinn #2," it's explained that the nickname was given to a non-Joker Jack Napier, as he is as classic as the dessert treat. He even jokes, "Please tell me that's not my new nickname," knowing that it's going to stick. Harley's insistence in calling him puddin' even when he returns to being the Joker is presented as her way to remind herself that he's still Jack underneath the makeup, and perhaps her attempt to remind him of who he is capable of being.
To contrast, season 2 episode 6 of "Harley Quinn" sees that it's Joker who calls her puddin' for the first time. She approaches still as the psychiatrist Dr. Harleen Quinzel, but the Joker mistakes her for someone else and says, "Hello, Puddin'." Quinzel is confused and says, "Puddin'?" with a meek, almost impressed demeanor, to which Joker then replies, "Oh s***, I thought you were the person who brought my lunch."
So why does Harley Quinn call the Joker a nickname that equates to her calling him a Snack Pack? It's up to your own interpretation.