When Dori mentions the dress Gloria is planning to wear, Arabella chimes in with a remark about how the dress will be blue. The color of the dress something Gloria had mentioned to Dori and Tommy, but not when Arabella was around.
Chuck Berry's electric guitar isn't plugged into anything when he performs on TV.
When the Johnny Burnette Trio is playing, the bass player is obviously faking. His positions on the neck are no relation to what should be played.