WARNING: The following contains spoilers for Batman: The Adventures Continue #16, by Alan Burnett, Paul Dini, Ty Templeton, Monica Kubina, and Josh Reed, available now.
Since the Harley Quinn cartoon made Harley and Poison Ivy an official couple, the two Gotham heroes have been growing closer together in some parts of the DC Multiverse. Some stories implied they might have had a thing in the mainstream DCU but in Elseworld tales such as Injustice, it's more out there as they actually got married. However, in Batman: The Animated Series, clues subtly suggested they were always meant to be more than friends.
Now, in the digital comic follow-up to that cartoon, Batman: The Adventures Continue, it's revealed that years later they're still very much in love, bringing their bond full-circle.
Batman: The Adventures Continue #15 focuses on Harley and Ivy at their apartment outside Gotham Plaza wanting to bring holiday cheer to fellow criminals. Here, they're all snuggly, cozy, and coming off as more than friends. They have affectionate nicknames for each other, with Ivy calling her "peanut," and Harley giving her gal a peck under the mistletoe or as she calls it "the kisstletoe." This signifies they're more than just besties, especially as Ivy is adamant about the "no exes" rule. Ivy doesn't want Joker ruining her party, especially as it's the one good thing they get to do for the year, and more so, she doesn't want Harley distracted by an abusive element of her past.
What's interesting is their dynamic throws back to when they first met in the "Harley and Ivy" episode and became the "queens of crime." While they got apprehended, over the course of the series, they wanted to help each other become better women and this seems to be the culmination of it all: perfect partners in a nutshell who listen to each other. It's not just about compliments and stylish praise, though, they're based in substance, truly caring for each other and mature enough to think of friends for Christmas.
When the party kicks off in Batman: The Adventures Continue #16, the couple is at the Iceberg Lounge where Harley actually gets jealous over Ivy inviting her fertilizer lady, Ms. Kwan. But Ivy's playfully pranking her, offering a kiss under the mistletoe to return the love she's showered her and everyone else with. At this point, it's obvious they're in the healthy kind of relationship that evaded them all their lives.
Given the involvement of several creators who were involved with Batman: The Animated Series or its comic book tie-ins, it seems like the couple would have eventually gone down this path on the '90s cartoon. After all, those episodes had them sharing a bed, constantly wanting to spend time together, giving us suggestive hints there was more to them than friendship, and this story all but confirms that they were always meant to be lovers.