You know, I've seen a lot of this kind of stuff in and around DA and I just gotta say it's such a relieve that I'm not the only one who thought of this, these two, in this kind of situation... What was the episode that started all this, or at least put the idea into overdrive? I think it had something to do with a glowing door and I remember Jake wearing jeans... meh, the title will come to me soon. Anywhoooo, I love this but not enough to favourite it, sorry 'bout that.
But this would never happen in the show because: #1: Marceline has already had a boyfriend, and makes other references to herself being attracted to "cute dudes" #2 While PB seems to be too busy for a relationship of the romantic sort, when she was 13 in the episode "Too Young" she expressed romantic feelings for Finn, who is obviously a male
However, I do love the colors and palette you used in the picture! You are a great artist!