During the concert scene with the hot blonde fan in the white fringe top, she throws down her old cigarette when she starts to dance, but a moment later, she's magically holding a new freshly lit smoke.
In the scene where Jerry Lee is picking Myra up at school, while singing "High School Confidential", she had a red ribbon in her hair. But in the next scene, which is supposed to be right after he's picked her up, the ribbon in her hair is grey with trombones on.
When Jerry Lee is playing at the Cotton Jamboree he pulls his coat off, but in the next two shots he is wearing the jacket again.
When Jerry Lee comes off the plane from New York, there's a lot of girls gathering around. One of them kisses his cheek right by the ear, but in the next shot the mark after the lipstick is far nearer his mouth.
The song "Great Balls of Fire" is shown climbing the Billboard charts to number one. The song only made it to number two.
When Elvis Presley shows up at Sun Records, he is shown signing an autograph left handed. Elvis was right handed.
There is a shot of the plane Jerry Lee is flying in from England to the United States. It clearly shows a TWA logo, yet when the shot jumps to Jerry Lee coming off the plane, the plane changes from white to silver and from TWA to American Airlines. However, the plane he flew across the ocean (London to New York) would not be the plane on which he landed in Nashville; there were no direct London-Nashville flights in the 1950s.
The song Jerry Lee performs in the United Kingdom is "I'm on Fire". While the setting for this scene was 1958, the song was not released until 1964.
When Jerry Lee is in England, the car he's in is being driven in a bus lane. The tour was in 1958, ten years before bus lanes were introduced in the United Kingdom.
When Jerry Lee plays at the burning piano, he stops playing clearly before the piano sound is gone. It keeps on a few more seconds, then it stops too.