"What Was Missing" is the tenth episode in the third season of the American Cartoon Network show Adventure Time. It is the sixty-second episode overall in the series.
The "finished" episode centers around Finn, Jake, BMO, Marceline, and Princess Bubblegum coming together to play music as a genuine band, in order to open the gate of the Door Lord and retrieve their stolen items.
There was a cancelled/banned version of the original episode that was being made, which was controversial due to it being focused on a possible romantic subtext between Princess Bubblegum and Marceline. It was originally produced by Dan Rickmers, and the only proof of its existence comes from the also-controversial behind-the-scenes video, "Mathematical!".
Only 30 seconds of the episode exist, all in the form of sketches. It's debatable if the episode was even animated.
In the behind-the-scenes promotional video "Mathematical!", it shows original behind-the-scenes footage that possibly focused on a romantic subtext between Marceline and Princess Bubblegum. The promotional video was removed by Frederator's Fred Seibert, and Seibert later issued an apology, which read:
"In trying to get the show’s audience involved we got wrapped up by both fan conjecture and spicy fanart and went a little too far."
On the Spring.me website, writer/storyboard artist Adam Muto stated that there was a problem with what the video did:
"If it was just a fan video there would be no problem at all. The problem was that it was made by a production company actively involved with the show. The video took something that was a possible subtext and declared it, in effect, text and made it seem like the production was actively seeking out input on plot development."
As a result of this situation, the "Mathematical!" video was removed from YouTube and Frederator's website, and Dan Rickmers was fired from Frederator Studios. Fred Seibert stated that the decision to pull "Mathematical!" was not influenced by the Adventure Time crew, nor by Cartoon Network. However, it has been reuploaded to YouTube numerous times.
In 2014, Marceline's voice actress, Olivia Olson, stated that Marceline and Princess Bubblegum did, in fact, have a relationship in the past, and that several other Adventure Times characters were also homosexual. It is doubtful that any animation of these relationships will appear in future Adventure Time episodes since the series airs in countries with extreme homophobic laws, such as Russia. This scene was also cut in Turkey and the Middle East.