What Was Missing

"What Was Missing" is the tenth episode of season three of Adventure Time.

Synopsis
The guys take on a door lord who steals Jake's blanket, Finn's piece of Princess Bubblegum's hair, Beemo's controller, and an item from Princess Bubblegum and Marceline. After stealing something from Marceline they must "do music" to open the door to where the door lord resides.

Characters

 * Finn
 * Jake
 * Marceline
 * Princess Bubblegum
 * Beemo
 * Door Lord

Songs

 * I'm Just Your Problem

Trivia

 * This episode was formerly titled "Door Jam." Adam Muto confirmed that it was the working title.
 * Doorjam.jpg storyboard piece reveals that not only will PB and Marceline meet again, they each have new outfits. At some point, Bubblegum will sport a more casual look with her hair in a ponytail and a hooded jacket over her dress. Marceline appears to have grown her hair back to full length and gained a pair of shiny, knee-high, heeled boots. She will also sport a large sunhat so she can travel by day.
 * Finn still has the wad of Princess Bubblegum's hair he got in "To Cut a Woman's Hair."
 * The storyboard was revealed prior to "Mortal Recoil" and the de-aging of Bubblegum to 13. Adam Muto, the storyboard writer, stated at the time of its release that this episode was created before the decision in that episode to change her age. However due to the events of "Too Young" returning Bubblegum to 18, this episode no longer has any problems tied to that adjustment.
 * According to the lead character designer Andy Ristaino, this episode is going to be a musical.
 * This is also likely the reason its former title was Door Jam, referring "jam," which has to do with music.
 * In the storyboard it says Finn "slaps lyrics on his backpack." This may be linked to the fact that this episode is a musical.
 * This is the first episode ever to be a musical.
 * There is going to be a guest voice. It is unknown who, perhaps the Door Lord, but he has done voices for the show before.
 * A five-minute preview of this episode was uploaded on the Cartoon Network website, which someone has ripped and uploaded on YouTube.