Factual error: After the part where they were at breakfast and discussing the idea of leaving early, you can overhear the radio and the announcer says, "Oh, those Mets! What a team! Finally broke their 22 game losing streak!" The longest losing streak for the New York Mets is currently only 17 games, which was in 1962, a year before the setting of the movie. (01:00:33)
Revealing mistake: In the scene when Johnny realises his keys are locked in his car and goes to kick the pole out of the ground there is a light on top of the pole. Where are the wires for the light?
Revealing mistake: When Johnny and Baby are cruising back from their performance in the black 57 Chev, the shift is in "park" position.
Other mistake: Under the Gazebo when Penny is giving a lesson to the group, the opening shot is zoomed in on people's feet. The 5th person is a lady wearing red kitten heels. When the picture zooms out to show the entire group, the lady with the red heels is gone. (00:04:40)
Continuity mistake: When Baby is getting dressed for the talent show, she is rolling down individual stockings, when she starts dancing with Johnny, there are no garters showing, even though her dress goes all the way up.
Other mistake: When Johnny breaks his car window, he is getting soaked but Baby is completely dry - her coat never gets wet.
Audio problem: During the "Hula Hana" scene, you can tell the little girl with the ukelele is only mimicking playing. A chord is heard being played in a staccato fashion, but the girl is merely rubbing her thumb against the body, and maybe striking the lowest string, while not fretting any of the strings with her left hand. Playing staccato on open strings would require you to use one of your hands to stop the open strings from ringing.
Continuity mistake: In the breakfast scene, the baby's hair starts off styled, then is teased up haphazardly, then is styled again.