The first episode of Adventure Time started in I think 2006 or 2007. In it, finn was originally called "Pen the Human" but was later changed to "Finn the Human" in 2010's pilot episode of Adventure Time. Adventure Time was created by Peneliton Ward.
Adventure Time started out with the original pilot episode. Later on the new pilot episode was made as part of season 1 in 2010. Then when they new more people started to like Adventure Time they made season 2, season 3, season 4, and season 5 of the show. Each season has about 26 episodes and each episode is about 11 minutes of adventure-packed fun!