Two things I'd like to point out.
Second off, the plot about a Reptilian Replicate PB intrigues me. Here comes one of my craziest theories yet.
This theory harkens back to that dark night of August 8, 2011, the airing of "Too Young". Basically, a group of xenophobic reptilians abducted PB just as she was about to become 18 again (the flash of light hides the act). In her place, an aggressive, love-less replicate of PB was inserted. Somewhere, out there, PB is still young, and is still being held by the reptilians in their secret fortress. Every night, she prays that Finn will rescue her and they can live a happy life together.
BTW, the reptilians are xenophobic against every single species. They hate everyone (even The Lich) and want to be the dominant species.
On that note, I'd like to mention I didn't make this theory.