I am a former intern that used to work at Cartoon Network. Around the time of my arrival, Adventure Time was about to air. The employees settled down to watch the Pilot episode, but what we saw was not the Pilot episode.
The episode began to air like a normal one does: with the theme song. It was the same except for when Finn and Jake pounded fists, the backround was red, not blue. At the end of the theme song, it said "Adventure Time" in a rather odd way, somewhat scarily. Followed by this, it showed Finn and Jake, playing Beemo. All of a sudden, a gothic-style Princess Bubblegum came in and in a rash voice said "Finn the Human Boy, Hell needs you!" Something was up. HELL? The directors and creator Penn Ward were shocked but decided to continue on. Finn, then said in Jake's voice: "Well tell Hell I don't need it!" He threw a glass bottle at PB and blood shot through her head. Jake, dumbfounded, tried to help PB up. But, Finn picked up the glass bottle shards and scratched Jake upside the head with it. "FUCK CHILDREN!" Finn screamed in a loud, scary voice. Penn Ward jumped and told everyone that the tape was messed with. It had to have been! Penn didn't write it, did he?
The next scene may shock you. Finn proceeded to go to the Slumber Party that was featured in the first episode. Ranicorn and LSP were there, along with the Candy People and Ricardio the Heart Guy. Finn ran in and yelled "FUCK YOU!" It then showed a picture of a naked kid with a knife through its mouth. A few workers ran out of the room. Penn and I, along with a couple curious writers stayed. Finn proceeded to take out his sword and slice already-dead Princess Bubblegum's throat. Blood went everywhere and the affects were way complex for Adventure Time. Finn proceeded to laugh at the killing of PB, in Jake's voice once again. Than, on the screen, it said "Hell" for more than twenty seconds, until a possibly live camera feed show a creepy, scarred, man whp was screaming "FUCK YOU" and other horrible things, along with threatening Penn Ward. And than, he switched to a different camera on the feed, showing an old wrinkly man raping a child. Both of them naked.
Penn had no idea this was made and feared to even cancel the show. But the man hasn't come back. Yet.