So I've rewatched all of Adventure Time except the sequels. And it's really good. In fact I think it's altogether my second favorite show after GoT. I give it a 9/10. This is based on my feelings toward the show as a whole, not a mean of all episodes, which would be much lower. The ideas, characters, and world building is just so strong. And it's remarkable that the characters are good given that the show is mostly famous for being insanely weird.
Because I like rating things, let's rate the ~12 most common characters
Finn. Good realization of a teenager. Straight-forward personality, but likeable.
7/10.Jake. So I don't think I really understand Jake, or how you could come up with him. One way to look at him is like an adult who chooses to never grow up/live a teenage lifestyle. If you do read it that way, then the show's verdict is that this is a totally fine thing to do, but it's unclear how to transfer that to the real world?
And the other thing is that he keeps doing random/unpredictable things, sometimes in really important cases. But it works out. And he's a dog, but it's adventure time so that doesn't really factor in.
I kind of don't like him as a person? But he's fun to watch. There must be something genius about him. Idk?
6/10.BMO. He's a cute robot! But actually, I think he's best read as an eccentric kid. He's into weird things and does weird games with himself when he's alone. And his thing is like... being fascinated by the idea of being human-like (or not-robot-like)? The show definitely made a point that he's programmed to understand fun, unlike other robots. Also arguably gender fluid? There's one episode where he imagines that his other self in the mirror takes his place, and also the other self is a she. And called Football because this is Adventure Time. Anyway I like him.
7/10.Lady Rainicorn. Chill, feminine, mature, and only speaks Korean for some reason. And she's Jake's girlfriend, and the show gets props for breaking stereotypes and not having a single scene where they have relationship drama. Anyway, the fact that she's this preposterous made-up creature but totally feels like a real person is cool.
8/10.Lumpy Space Princess. So. This character. She's a bratty, entitled, naive and ridiculously self-centered uh princess. But she's also a flying purple ball, which somehow makes her brilliant. I can't really justify it, but I feel like every scene with her in it is hilarious. Maybe because she's somewhat self-aware and tries to be good when it really matters, so she's really likeable? Or maybe because she's so wonderfully authenatic? Anyway she's great.
9/10.Marceline. I believe she's probably the most universally beloved character of the show. She's supposed to be 1000 years old and a vampire, but who chooses to live a fun lifestyle.
Whenever extremely old people who have a young physical appearance are depicted in fiction, they tend to be awful. The most common failure mode is make them behave in ways that are totally unrealistic for someone with this much life experience. However, Adventure Time happens to have good writing, so Marceline avoids this completely and manages to be believable. And beyond that, well, she's cool and a lot of fun.
9/10.Tree Trunks. This character. What to say about this character? Well let's start with the obvious. She's an idiot. That's kind of her main character trait: being unintelligent. She's also incredibly condescending and self-centered, but totally not self-aware, unlike LSP.
I feel like the show understands this since her character is fairly consistent. E.g., she unironically admires the next character, which I find highly believable. But at the same time, the show gives her a pass? She should be treated like the piece of shit that she is, but she's not. She's instead treated as real character, which is extremely annoying. She tends to make every scene worse by being an idiot who others have to deal with, but since they treat her as if she's decent, it's annoying rather than funny.
So basically what I'm saying is that she's the worst character ever and I hate her. Yet she keeps being brought back. There's an episode about her in the final season. I don't know why. Tree Trunks is abysmal. She also has an incredibly annoying voice.
0/10.King of Ooo. This character's personality is that he's a piece of shit. That is literally it. He's acting benevolent to others, but it's made perfectly clear that it's purely an act. He is power hungry, money hungry, status hungry, has zero empathy, and acts entirely selfish. This never changes, there's not a single scene where he does something for someone else or is redeemed in some other way.
However, none of this is bad since he's treated appropriately by the show, so actually, I think he's a pretty great villain. He doesn't appear that often, but I like basically everything they did with him. Good stuff.
8/10.Susan Strong. So she's introduced as a primitive, sort of barely-above-animal-level-intelligence human, but actually she's a smart educated person whose brain got messed with. There's an entire huge backstory about the other humans relating to her, about which I mostly felt the same as I feel about this character, which is that she's not terrible but doesn't have anything particularly going for her. She's just kind of boring compared to other things in the show.
4/10.Princess Bubblegum. She's the Candy Princess! That means she's literally made out of candy, and she's the princess of the candy kingdom, where everyone else is also made out of candy! And she's all pink and girly. Woo.
If this show were bad, that would be the extent of her personality. She would be dumb and pretty, and Finn the main character would have to do things for her or whatever.
But the show isn't bad, it's Adventure time, so she's a real character. She's also the incarnation of the candy elemental, which in this universe is one of the four primal forces in the world. 800 years ago she was created along with her brother, who is a barely sentient dragon creature afraid of everyone except her, but who has the power to turn vitamins from trees(?) into a substance that's sort of a universal life force.
So being the only intelligent person out there, she began studying her environment, built stuff, and literally figured out how to use the life force to create candy mass and then give it life. So she's not only the person who actually runs things, she also literally created every person in her kingdom. Instead of being dumb because she's a pink princess, she's easily the most intelligent character in the show and -- gasp -- actually makes smart choices consistent with that, well most of the time. She's also a control freak who spies on everyone all the time to prevent disaster, and it's mostly working.
There's a sub plot early where Finn is romantically interested in her but -- get this -- the show understands that an 800 year old scientist who is running a kingdom isn't going to be interested in a teenager. I know, I can barely believe it myself. Instead, she eventually has a romantic relationship with Marceline. Someone roughly her age.
And also, besides being ancient, brilliant, and the creator of life, she's also a totally believable cool person.
The fact that it subverts expectations so much does make it better, but she'd be amazing even without that.
10/10.Gunter. Wenk.
8/10.Ice King/Simon. So Simon is a nice, caring, somewhat nerdy bookworm, but he found the ancient crown which turned into... well, Ice King who you see on the left. Who is so different that it's not really possible for me to conceptualize them as the same person, they're just two separate characters in my head.
The show severely messes with you by introducing Ice King first without telling you about the backstory, and when they first do, I remember assuming that it was a pretty messed-up joke that would never be brought up again. It wasn't. They totally went with it.
So Ice King, despite being ~1000 years old, is best thought of as something like an autistic kid that wants to make friends but no-one likes him. The crown basically kills his long term memory, so he lives on a couple of month(?) long time horizon, and because this show is well-written, that tracks how he behaves. Also, he kidnaps princesses. which is funny.
Kind of difficult to critique them since Simon doesn't have enough screen time to be a real character and Ice King is, well, mostly functioning by creating problems for everyone else to clean up. But I always thought the crown thing was really strong. Also, he's a lot of fun as Ice King. The episodes with him in it tend to be great.
9/10.Earl of Lemongrab. Describing this exceeds my abilities, but for whatever reason I actually think he's fantastic.
9/10.