 DATE: Jerry Lee Lewis, who sings right before Johnny Cash on the  first show you see, wasnt famous at the time. In the movie "Great  Balls of Fire", Sam Phillips says that Jerrys going to be "bigger  than Elvis and Johnny Cash", implying that Cash was famous already.  However, when Cash in playing in Walk the Line for the first time,  he had only had one hit, and clearly not used to the stage.