'Adventure Time' EP Shares Behind-The-Scenes Details on That Long-Awaited Kiss

Adventure Time made one of the most beloved cartoon ships canon on Monday, and an executive producer says that it was not a simple decision.

Warning! Spoilers for the Adventure Time series finale lie ahead!

Adventure Time came to a thrilling conclusion on Monday with its series finale. The franchise has been known to push boundaries and break conventions, but many never dreamed that it would succeed in putting a same-sex romance on the screen. Still, in those final moments, Princess Bubblegum and Marceline shared an earnest kiss, bringing many fans' dreams to fruition.

In an interview with TVLine after the fact, executive producer Adam Muto discussed how it came to be. He said that it had "been an ongoing conversation" among the writers and artists working on the show. He named one writer and one artist in particular who made the kiss happen: Rebecca Sugar and Hanna K. Nyströmthe.

"It certainly wasn't in the show's original pitch," Muto admitted. "It was a relationship that evolved over time."

As far as Muto is concerned, Sugar put in the work needed to build a foundation for the relationship many die-hard fans refer to as "Bubbline." Sugar was credited as a writer on Adventure Time from 2010 to 2015. From 2010 to 2013, she also worked as a storyboard artist and storyboard revisionist.

In that time, Muto says she was "building and nurturing that connection" between the two characters. She even provided the voice for Marceline's mom in the episode "Stakes Part 2: Everything Stays."

Meanwhile, it was Nyströmthe who who drew out the scene where Bubbline finally came together. Muto said that the writers, producers and artists wanted Bubblegum and Marceline to "have a moment," but Nyströmthe decided it would be a flat-out romantic kiss.

"There was some conversation about [logistics], but it was really up to [Hanna K. Nyströmthe], the storyboard artist who got that scene, to decide what her take on it was going to be," Muto admitted. "It actually wasn't in the outline when it was submitted. It didn't say that they kiss. It just said they 'have a moment.' When Hanna boarded that, there was a little note in the margin that said 'Come on!' with a big exclamation point. That was the only note. I can't argue with that."

Adventure Time was created by Pendleton Ward for Cartoon Network. It finished its remarkable run on Monday, with a total of 10 seasons and 283 episodes.