The Fairly OddParents - 2x06b - The Boy Who Would Be Queen

Hoping to find the perfect gift for Trixie Tang's birthday party, Timmy wishes that he could think like a girl, but to his horror he is turned into an actual girl named "Timantha". Using this temporary change to his advantage, Timmy heads to the Dimmsdale Mall where he bumps into Trixie while browsing. To Timmy's surprise, he learns that Trixie secretly likes the same things boys do, and finds out that the only gift Trixie wanted was a real friend.