You know, when you first see the Ice King, you'd think he's just a petty antagonist.
Then you learn him and Marceline's past.
And then tears fall, with so many thoughts in your head (Oh god, I'm so sorry I didn't think of that, I'm sorry) and realize you had misunderstood him.
(You know, if he were to remember who he really is... Would he be a coward and run away? Or face the truth and apologize?)