The Adventure Time episode, What Was Missing, was on the other day, and that episode has the best songs so far. 

The song that Marceline sang, I’m Just Your Problem, was perfect. And Finn’s song, My Best Friends in the World, was so enjoyable and I love singing along to it. The only thing they messed up with that song was having Marceline sing along with Finn at two very random parts. It wasn’t really in sync for me… 

That’s just my opinion, though.