There are a lot of "Adventure Time" theories out there, but one of the biggest is apparently a bunch of hooey. Or as Lemongrab puts it ...
When talking with HuffPost Entertainment about the new SpongeBob movie, actor Tom Kenny, who also voices Ice King on "Adventure Time," debunked the theory that claims "Adventure Time" is really just a bunch of bedtime stories that the Ice King reads to Marceline.
"For me, that’s interesting, but I like to think Ooo is its own world the way Bikini Bottom is its own world," said Kenny. He continued, "Ooo is a very interesting place and Pendleton Ward is a very interesting dude, and I don’t like to subscribe to theories that invalidate the world that you love going to. So, nah, I don’t buy that one. It’s too cheesy. 'And it was only a story told by the Ice King.' Boo! That feels like a rip off."
The theory, which has been reported by a variety of sources, began gaining popularity after it was revealed that Ice King and Marceline had a past together that fans didn't know about. The episode "Simon & Marcy" tells us that around the time of the Mushroom War, nearly 1000 years before "Adventure Time" takes place, the Ice King was known as Simon Petrikov and cared for young Marceline.
Evidence that supported the claim that "Adventure Time" is just a bedtime story includes the fact that episodes usually involve some sort of moral lesson and Ice King is a known storyteller, as demonstrated by the fan fiction he writes.
Though it seems like this theory isn't true after all, you homies don't need to fret. There are other theories about the show that you can get behind, including one that claims "Adventure Time" is Finn and his dad's role playing game and another that says Finn is actually in a coma. (That one is kind of along the lines of that big "Simpsons" theory.)