It's been exactly a year since the controversial Adventure Time episode "What Was Missing" aired, with possible implications that PB and Marceline shared something a little special in the past... perhaps more special than Finn's crush on PB? ;)
This possibility has been the cause of much debate, but Bubbline remains a symbol of hope for the LGBT community that one day they WILL be accepted by society and won't be monopolized or tormented by religious fundamentalists or general homophobes. If we can teach the younger generation that homosexuality isn't a sin, while this younger generation hasn't yet inherited homophobia, then we can hope that the future will be more tolerant and we'll benefit more in general because there would be less LGBT members thrown onto streets be their parents, or killing themselves because they get bullied in school, etc.
As of right now, the AT staff have been VERY quiet on the subtext, and it is still possible that the two used to date or that Marceline had or has a crush on Peebles.
So, here's my celebratory post with all of my fanart on the ship:
(Most of this fanart was done in June and all of it was done before August, so yeah, it's pretty old.)