Just click on Rapunzel's hair in one of the scenes ( I don't remember which one, sorry). You need find a special spot. A small sun should appear on the screen. After end you need click on hair in main menu.
Every scene must have the sun.Click anywhere on Rapunzel's blonde hair.It will happen when there are 3-4 suns.Except for the conversation with his mother in the last scene, the others have the sun.