Justin actually made this as a way to poke fun at the idea of getting cease and desist letters.
At the time (October 2006) he had nothing to lose and his original intention was to call this "back to the future: the new official universal studios cartoon featuring the new Doc Brown and Marty McFly" and then just sit back and wait for a letter from their lawyers to arrive. That's actually why it's so filthy. He was just looking to "troll" a big studio.
7 years later, hit new animated TV show on adult swim.