In the season 3's "Thank You" Finn & Jake beat up the Ice King, and nearly at the end of the episode when the Ice King is restrained Jake takes his crown and wears it:
It's been said and shown in other episodes that the crown has certain "efects" on whoever wears it. That's what made the human Simon Petrikov into the Ice King after all, the same goes for Farmworld Finn.
How come that has no effect on Jake? Is he maybe immune to the crown's powers because he's a magic dog?