Ok. so this may look old but in the frost and fire episode were finn dream about flame princess (1st day) then ice king (2nd day) hoth looks like attacking finn with cosmic owl, I have a theory on that, so as you can see finn is the one who cause the fight right? But what if the reason why finn is the one who get attack in the dream is that because he is the one that should stop thinking about it and prvent the fight from happening, so you see before the sad ending finn has fall asleep for a while then he see again cosmic owl looking at him and saying that he messed up. Maybe the cosmic owl wants him to prevent the fight insted of causing it (which is what he do he wrote letters to both flame princess and ice king si that they could get angry at each other then fight). maybe the cosmic owl is warning him to prevent the fight.