When it comes to the Princess & the Frog in Disney's version Prince Naveen is being cursed as a frog. In order to break the curse a princess has to kiss him. When Tiana kisses the frog it turns her into a frog as well. You know the rest of the story.
In the real tale some of the early versions of the Princess and the Frog the curse is broken when the princess hurls the frog into a wall. Other versions of this tale are the frogs head is either chopped off or his skin is burned.
