BUBBLINE LIVES! Well, sort of.
... that at some point in time Princess Bubblegum and Marceline TOTALLY WERE A COUPLE.
Olson answered a fan's question (cut off in the video) concerning Bubbline, referencing a conversation she had with creator Pendleton Ward.
"And he said, 'Oh, you know they dated right?'"
Here's another video of Olsen answering the question with one fan yelling, "YES, YES!" as she spills the beans.
WE HAVE REACHED CANON. I repeat: We have REACHED CANON.
In the video you can see Olsen also made a point to ask Ward if the couple would be visible on the show or in the upcoming book. Unfortunately, not so much.
And I said, 'Are they going to do it on the show at all, or can we say anything about it in the book?" And he's like, 'I don't know about the book, but in some countries where the show airs, it's sort of illegal.' So that's why they're not putting it in the show.