This is a preview (which is basically the first five minutes of the episde) from Cartoon Network's website for an up-coming episode of Adventure Time. The summary of the episode, called "What Was Missing", is as follows:
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 he steals something from Marceline, the gang must "do music" to open the door to where the Door Lord resides.
The episode will air on September 26, 2011.
I'm really curious to see if this gets developed on any further, but mostly I'm shocked they were able to get that song on the air to begin with. Holy subtext, Batman! Actually, forget subtext, that was flat-out text. Kudos, CN.