I’m not sure if any of you have seen any of the interviews (like here and here) where Pen talks about his influences on Adventure Time, but I found two of three particularly revealing. The Simpsons is a given (it’s been around since Pen’s childhood).
D&D is best left for someone other than me to talk about. “D&D inspires my logic for how I go about creating each episode,” Pen says to Rene Guzman at the San Antonion-Express News. “In D&D, everything’s in front of you, you can do anything you want, it’s all up to your imagination. I like the freedom of that feeling. I like the characters to be able to have the freedom to segue away from a story if they wanted to.” Finn is “quite the justice-seeking righteous paladin.”