Chris Colfer
Colfer originally auditioned for the role of Artie, which went to his co-star, Kevin McHale. But "Glee" creator Ryan Murphy was so impressed with the actor that the Kurt Hummel character was created for him.
Part of that episode's plot was drawn from Colfer's experiences - during the episode, Kurt is criticized for wanting to sing "Defying Gravity," a song traditionally performed by a woman. Colfer said that when he was in high school, his teachers wouldn't let him perform the song in the school talent show because it was a "girl's song."