Well, what do we have here? A dash of Bubbline for your souls.
Today (well, as of this very minute, yesterday) I watched the Adventure Time Comic Con panel on youtube and I was just WAITING for somebody to pop the Bubbline question, and when they finally did the reaction from the panel was pretty hopeful.
Audience member: "Was there a romance in the past between Marceline and Princess Bubblegum?"
*Audience goes WOOOOOOOOO*
Pen: "There's a lot of fanfiction on that subject."
*audience laughter*
Rebecca: "I don't think it's any of your business."
*Audience goes WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO joyfully*
So the implied past romance between these characters has not exactly been denied, and the protectiveness over this subject from the panel means that they actually care about the huge number of fans that consider this past relationship canon (it's probably the most popular ship for the entire show) and don't want to break their civil-rights-seeking hearts yet. ("Burning Low" might do this for them.)
In any case, I think that children's television is LONG overdue a representative 'normal' homosexual relationship, and Adventure Time is currently the best, deepest cartoon on TV right now with the mot amazing female characters I have ever seen, so what better cartoon characters to break the chain of cartoonized homosexual stereotypes than PB and Marceline?
I've been wanting to draw these two in a fluffy but in-character pic like this for a very long time now. Most of the fanart of them is either too sexual or too out-of-character, so the best fan-artist for them I have ever seen is

with his truly epic minicomics.
Okay, this is NOT the full picture of the Scream Queens like I promised, but I was far more motivated to do this than continue that one yet.
I cannot exaggerate how difficult it was to draw Marceline. First of all her (failed) hair caused me difficulty, then her LEGS caused a hell of a lot of issues because of the positioning.
She's gripping a piece of PB's hair and PB is annoyed.
PB is wearing an outfit not dissimilar to the one she wears at the end of the first 'Scream Queens' comic.
Done on Microsoft Paint 2003 on a faulty laptop mousepad. No tablet or anything yet, just crappy stuff.