YES, A CHANCE TO TALK ABOUT ADVENTURE TIME!
I'm just going to talk about Finn because this would be SO LONG if I were talking about everyone (or just him and Jake) and I have history homework to do. I don't care that he's not an underdeveloped character or whatever but I just think people see that one [tells joke] [is boy] storyboard and kind of say that's all he is. Hell, he might not be the best or most well developed character despite him being the MC (I mean Simon, BMO (yes BMO, if you disagree please watch Be More and The Moe you Moe the Moe you Know), Jake and Marcy are right there) but he's amazing and my special interest so I'm going to talk about him.
Obviously, Finn is great. I'm even slowly creating a cosplay of him. I love how despite looking the same (other than his arm ofc) he develops so much emotionally throughout the show. He goes from an immature pre-teen to a guy who really knows his stuff and understands how to be kind, and it's pretty admirable.
His relationship with FP (flame princess) is absolutely the best way to highlight this. Comparing Frost and Fire to the other times he sees FP toward the end of the show but especially Bun Bun is a genuinely heartwarming difference - in Frost and Fire you see how much he's willing to sacrifice her happiness and even her health just to finish a dream that might not matter (yes the cosmic owl was in it but it didn't mean he had to see it through all the way), but far more importantly his inability to grasp the gravity of the situation or apologize properly. The episodes after that where they meet again, it's got some good ol' post-breakup teenage awkwardness, and as much as other people might hate these episodes they show growth - at the end of them he's able to move on and is starting to realize what he's done. In Bun Bun, when they meet again not only are they really caring and starting to build a proper friendship, with Finn giving a real apology and her accepting it (the acceptance is the most important part, the entirety of his development shows he wouldn't have pushed her to if she didn't want to and that he completely means it). She even meets him without her guards around and out of her armor - and Finn would have too if not for the heat of the flame kingdom - and it shows how open she is to talking again, with them getting on pretty well even with the context of their past relationship.
It's really sweet, honestly. In Son of Rap Bear (an episode that I absolutely did not appreciate enough when I saw it the first time), they're amazing together and it shows how much they've grown. It just leaves you wishing them the best and hoping that they'll stay close friends behind the scenes, and the episode being filled with the same humor from the earliest parts of the show after some crazy stuff going on in Finn's life demonstrates to the audience how even though they've both grown up a lot it doesn't mean they're not fun (plus it's cute and nostalgic).
Another great example of this is with Martin (his dad). The episode where he wants to tear off his arm is a really low point in Finn's life. Yes, he's defeated the Litch King, but he can't even celebrate because he just lost his absolute dumpster fire of a dad, and even though he wasn't good to him he was his bio father and that was important. Of course he loved Joshua, but he just wanted to meet another human that was related to him, and Martin didn't even care enough to say a proper goodbye. (Yes, Martin's character is more complicated than that - he sacrificed a lot for Finn in the past as shown in later episodes - but he's done some horrible things and those can't really be fixed.)
The fact that Finn's sense of vengeance gets to him isn't even unexpected or a necessarily bad character trait - hell, if someone tore off my arm I'd get theirs too - but it's all there to cover up how badly he wants everyone to love him and to see him for the guy he is, instead of calling him immature (PB is guilty of this at times, and sometimes she's right but it does wear on him) or making him do everything for them (*cough* *cough* LSP (as much as I'm not a fan of her she is absolutely iconic tho)) and him being able to tear off his dad's arm in some way in the tower (thanks PB) finally gets it through his head that he just wanted to be loved and he's now "neutral".
And then when he finally gets a chance to do anything he wants to Martin after he extorts an entire planet of innocent people? Hurt him, kill him, even? He's just Finn. He sends him back to space and lets him go. He hates him, but he won't let Martin harm anyone or affect his emotions too much. And then in In the Comet? They have a... cordial sendoff. Finn beforehand would have clung to him or pushed him away entirely, but here he's okay with it. They end on pretty decent terms, all things considered, and no more arms get ripped off. Later on he describes his dad as a crummy dude when asked if he's evil or not, and you know what? I think most people would do a much harsher job describing him (myself included) than that. But he lets it go, and he focuses on what's important instead of letting it build up in him, and that's the important thing. Unlike in the tower, he doesn't let anger overwhelm him, which is pretty impressive if you ask me.
I'm running out of time and those were my top two that I don't think are talked about enough, but I'll give some quick examples in no particular order.
- his development after Fern's "death", learning how to overcome grief (super common topic)
- him understanding fern at the end of the show and both of them reconciling (obligatory inclusion)
- his acceptance of "the vault"
- him rejecting his mother if it means that he can save others, something that he struggled to do with Martin
- him realizing that a romantic relationship with PB isn't possible (especially after he realizes she's not 19) and moving on, even though he does so slowly
- him becoming more content with his arm and even taking the prosthetic off in spinoffs/smaller eps
- THE HALL OF EGRESS, ABSOLUTELY WONDERFUL EP
- in the same vein as the hall of egress, dungeon train
- the ep where he learns to use his imagination more often (this is fairly early on but he never regresses back to not using it and that's kind of admirable)
- him becoming nicer to Tiffany at the dentist and understanding her need for attention, even if she isn't nice to him
- him having a really healthy relationship with huntress wizard
I'm definitely missing things, but thanks for reading!
TLDR - finn cool