So I just watched too young, and i think, there was something seriously important... Here it is:
Jake said something when he was playing his video game, and I think it was foreshadowing. He said Finn would have to defeat the demon lord, maybe travel to different worlds, take his magic key from the water world, walk up the wizard stairs and give the princess a smooch.
GET IT??? The demon lord is the Lich! And Finn is already traveling to different worlds. And smooching the princess... Now it could be bubblegum, considering it was in the episode "Too Young" which is a fubblegum episode. but it could as well mean it's Flame Princess. I don't know, but I think there's some serious foreshadowing happening here...