As the seasons pass by, one of the oldest characters in the series still has a rather mysterious past. Princess Bubblegum (PB) has eluded the spotlight of theorism because honestly, she is kind of the boring science nerd that has a rather concrete style of thinking.
I could not settle for this. I’ve noticed that the smallest traces of PB’s past are hinted in her interactions with The Vampire Queen, Marceline.
I rather like this theory, but it seems a bit unrealistic, because Marceline says she was 1000 years old, and Bubblegum says she’s 18-19.