The show matured with its audience and every character had some sort of development. There was so many interesting and likeable characters, and all the places of ooo were so diverse and intriguing. The plot was always fun to follow and the filler episodes were some of the best ones in the series! The art style wasn't meant to be gorgeous, but that's why its simplicity was such a beauty. Some episodes were rather, "eh," but that's really the worst it got. Also, I personally liked this but the episodes could get heavy and somewhat disturbing in a way. Like in the season four finale when the lich (Pretty big spoiler by the way...) kills Billy and steals his body to trick Finn and Jake to open a portal letting him wish for the destruction of all humanity or something like that. Or in come along with me (The shows finale) when Betty (Another big spoiler btw...) sacrifices herself to become one with glob to save Simon and the world itself. On the other side of things we have a dog singing a song about baking pancakes though. Some parts of this show were truly a masterpiece...