The creators actually said that PB and Marceline once dated. So, this might mean they're hooking back together
Adventure Time Theories - lemongrab is weird
Adventure Time Theories
this kind of says the same thing as the one from before, but that one goes into more detail specifically about her mother.
adventure time theory | Cannot be unseen- Adventure Time fans by SkitzOpheliac on deviantART
"Interesting Adventure Time theory I found." Very deep. With Adventure Time you never know... but it would make a crazy adventure time kind of sense.
adventure time enchiridion - Google Search
that is a good reason why she doesn't have any eyes i thought she was scary at first but i realized that it wasnt that wierd you would need to warm up to her looks
adventure time theory | Adventure Time Theories (Submitted by stripes-redskinnies-toms.)
adventure time theory | Adventure Time Theories