LISTEN UP I'M NOT FUCKIN' AROUND
I love this show because if you can realize subtle things (for little kids at least), it suddenly turns into a different show.
For example, the land of Ooo is earth after a nuclear war. All throughout the scenery of the show, if you can notice little thing it's obvious this little kid show takes place in some kind of post-apocalyptic realm. They're are actually references to this hidden within the show. Finn and Jake will refer to things being "re-invented", and say things about "the time before magic" Not to mention un-detonated nukes. It's funny because no-one ever confirms it.
Another example (copy pasta) Finn and Jake's tale starts inside Lady Rainicorn's house with Jake bringing Finn a book he found that he believes is a warlock spell-book, which is actually an old pre-war book of nursery rhymes, from which Jake reads "Little Jack Horner," believing it to be a spell
The replacement curse words are also pretty funny in my opinion. Such as "lump" for fuck (lol) and "glob" for god dumbhole like dumb ass, and ass hole. LOL comon guys that's gold.
It also makes a large amount of hidden dirty jokes which honestly just get awkward. I'm not kidding, the characters actually will stand their and act awkward for 5 seconds after these jokes are made.
Also some episodes are just about plot holes in the show itself as if it was a joke, a It'll also get pretty creepy outta nowhere. The sex references are so common when you watch alot you're not even surprised when you find one.
Also a lot of pretty funny violence, The portal to the underworld looks really disturbing.