The "Happy Ending Song" is a song sung by Marceline the Vampire Queen, and is dedicated to 'someone who is special to her'. The accompanying music video, made up mostly of animated chalk drawings, highlights some of the key moments from the series, with the general gist being that she and her special someone get a happy ending. Throughout the video, scenes almost exclusively featuring Marceline and Princess Bubblegum run, and the final scene of the video depicts two figures together on a cliff.
| Run away, with me.|
And the poltergeists and ghouls,
We can wander through the darkness and play by our own rules.
Run away, with me.
| To a cavern shaped like home,|
Where we'll build our own forever,
and never dance alone....
- This song has never been sung in an episode. It is currently unknown if it is an actual song that will appear in a future episode or if it is from a deleted scene of "Marceline's Closet."
- This song is a parody of the ending theme sung by Ashley Eriksson.