Quote from Luke in Schooled
Claire: Luke, come say good-bye to your sister. Luke: [muffled voice] I'm right here. Bye, Haley. Have fun. Don't drink too much beer and shots of Tequila. Haley: Why are you wearing that mask? Luke: Uh, I like it. Claire: He doesn't want you to see him cry. Alex: He's literally masking his emotions. Luke: No! Haley: That's so sweet. Come here. Luke: It's not sweet. I'm an evil cyborg. Half my face was burned off in an industrial accident, and the mask is hiding the servos that control my mouth.