Not Sure I Understand

While watching "John From Cincinnati" the other night, I wondered something.

You see, there is a character with a facial defect. His female counterpart on the show refers to him as "The Hairlip."

My question is: How do they cast for such things?

Casting advertisement example:

WANTED:
Person who is not afraid of being made fun of for their hairlip.

Kudos to those who take the cash and are comfortable with their "issues."