Have you ever wonderd why Ice King's (Simon) purpose is to steal Princesses?Well,i came up with a theory.In the Episode "Holly Jolly Secrets Part II", Simon says this - "Just watch over me until I can find my way out of this labyrinth in my brain and regain my sanity. And then maybe Betty, my princess... maybe you will love me again. Please love me again, Betty!".
As you can see,Simon calls Betty his "Princess".You see where im pointing at,right?Now,the strange thing is,that you think "If Simon has only one girl that he loves,then why does he steal other Princesses?".In the episode Evergreen, Urgence Evergreen says that the crown he made can the one that wears it "Its One Greatest Wish".As of i just now thinked,Simon's one great wish was possible without even the crown,to happily live forever with Betty.But once he put the corwn,he turned insane.Betty was so scared from him,that she escaped.Siomon's now one great wish was to bring Betty,Princess Betty back to him.As of we already know,Betty is in the future timeline where Simon is already Ice King,searching for a way to make Simon Normal again.
Wondering why he loves the most Princess Bubblegum but not Doctor Princess?Princess Bubblebum look the most like Betty than the other Princesses.Look where Princess is. "Princess Bublegum", "Doctor Princess".The Princess Part in Doctor Princess is just the family name of the Doctor.For Simon,Princess is a title that his Betty deserved.
Why Didnt Simon turn to look exactly like Urgence Evergreen?The only reason i could think of,is because of his Willpower.The dinosaur Gunter didnt have enough to control the Crow,so he turned entierly like Evergreen,and became insane,only saying "Gunter No!Gunter No!Gunter No!Gunter No!"
Ice King Had More Willpower than the Dinosaur Gunter.He isnt enierly Insane.He only cant rember the name of his special Princess.
And as a little bonus that i will add to this theory,Finn had the most Willpower to control the Ice Crown (As shown by the only people for now to have wore the crown).His hair only grew a little longer,and his eyes turned Blue,but beard didnt grow on him.At times,he know what he was doing and he could control himself,only because he is a warrior at Spirit.I hope you liked my theory guys.