Princess Bonnibel Bubblegum is the tritagonist in the television series, Adventure Time and love interest of Finn Mertens and Marceline Abadeer's current girlfriend. Due to the huge age difference between her and Finn (She's 18 and he's 13), she doesn't return the feelings, though she does care about him. She's the Ice King's favorite princess to capture so Finn often saves her.
After the events of Mortal Recoil, she was blown apart after she had to be frozen by the Ice King to stop The Lich and she fell. Because she is literally made of bubblegum, doctors put her back together but they only had enough to make her 13 years old again. Once she is 13, she finally returns Finn's affections and they become a couple. However in "Too Young," the very strict and sour Earl of Lemongrab takes over the Candy Kingdom until Bubblegum turns 18 again. After a series of pranks performed by Finn and Bubblegum, the humorless Earl sentences everyone in the Candy Kingdom into the dungeon for a million years. In order to stop him, Bubblegum decides to turn 18 again revealing that she could have turned back to 18 anytime she wanted but never got to enjoy her childhood. The candy people give Bubblegum pieces of their candy flesh and Finn uses his saliva to hold them all together. Before she turns back to 18 she and Finn share a kiss. Since her return to 18, Bubblegum has stopped returning her feelings for Finn, though Finn is still in love with her and remained hopeful until the episode Incendium, where he develops a crush on the Flame Princess, wich she seem to not accept and finally begun to maybe see him more then a friend, but know it might be too late..
Princess and Marceline also had a romantic relationship before the show. It was revealed at a con.
In the episode Don't Look, Finn and Bonnibel are now friends.
In the series episode finale Come Along With Me, Bonnibel and Marceline share their first (onscreen) kiss.