I would just like to discuss the different ways that different characters are developed cause I'm bored.
So Finn is a pretty typical, straight forward kind of development, for a character of his age. Rather than having a personality that is slowly revealed through-out the show, his personality changes because he grows and learns. For the most part, it changes for the better, except for when he's readin' up on trash dating books by Jay T. Doggzone xP He grows as a hero and learns a lot of important lessons. The thing is, he gets very little backstory, which sets him apart from some of the other characters, but with him, it's not really a piece of development that's missing, it's more of something we just don't need. Frankly, there's only one thing we all want to know about Finn's backstory, which is his parents.
Jake also has a traditional development style, but slightly different from Finn's. With Jake, he has a personality, but it's slowly revealed to us throughout the show. He usually doesn't learn much and we mostly just see what he's like, how he relates to people, etc. He's actually a pretty great hero, inside, but he's too lazy to use any of that heroism and usually just passes some of it onto Finn when it's relevant. He doesn't usually get the hero's rewards, which is OK to him because he mostly doesn't care. He gets slightly more backstory I guess but there are things I think we want to know like where he got his powers.
PB is one of the characters in television history that I respect the most for her personality and the way it is developed. With PB, there's plenty we want to know about her backstory, but we don't get any of it because, rather than get massive amounts of backstory in all her episodes, Prubs gets massive amounts of personality development! It's crazy to see the kind of stuff she'll do for others, how she feels about all her friends, etc. We get lots of backstory through "hints" though, like whatever happened with her and Marcy, her age, and the gum in Simon and Marcy. I'm not saying it's necessarilly her, but how does it relate to her? Anyways, I love the way they give us her personality and how much more of it there is to see.
Marceline is developed in a completely opposite way from PB. What they did with Marcy was, they gave her a personality in Evicted!, explained it some more in Henchman, and then fed us backstory development in the rest of her episodes, mostly. Normally, this would be very boring and one dimensional, but what's great about it is, her backstory is what gives her personality! Sure, we've seen her personality, but her backstory helps us understand WHY she has it which completely opens it up even more! Like her anger is clearly pent up resentment against people like her dad and Simon, which we learn in "It Came From the Nightosphere" and "I Remember You". Or what about her hatred and how emotional she is, which we know from whatever happened between her and Bubblegum. There's still plenty of backstory to be revealed, which means plenty more personality.
Ice King's development style is similar to Marcy's because he is also given a personality that is explained through backstory, but it doesn't strictly rely on backstory. For awhile, he had no backstory. He got lots of personality development in episodes, though his personality was mostly pretty clear from the start since he's very eccentric. But then we got a huge mind bomb dropped on us and we learned a lot of personality through backstory episode, but still get personality development episodes from him, since backstory episodes for him are only occasional.
Anyways, these are just my thoughts, share yours and you can talk about other characters, but I only did the main ones cause I'm very tired...I think. I don't know, my right eye is in serious pain and it's starting to tear up and twitch. I don't really feel tired...help me.