The homeless man's stunt dick. The stunt face takes care of all the acting/oral in a porn movie before the stunt dick takes over for the money shots. Blest with a handsome face, but small wiener, the stunt face is forced to gnaw his way to fame.
If Tom Cruise (Top Gun, Cocktail) and Gheorghe Muresan (former Washington Bullets star, My Giant) were cast in a porno, Tom (the stunt face) would read the lines about delivering the pizza with extra sausage or whatever and then eat the woman out in a few tight close ups. Then, using movie magic, Gheorghe would step in to sexify the woman with his larger boner and proceed to blow his love juice on her face and chest. You'd never know two guys were in the movie if you watched it at full speed and skipped all the bonus extras on the DVD.