Continuity mistake: In the scene where Judy Garland and Fred Astaire go to the nightclub to see Ann Miller, Ann invites Fred to come up and dance with her. When she is dancing by herself, she is wearing red high heels. When Fred comes up, she is wearing red flats.
Continuity mistake: When Hannah and Johnny meet and are huddling outside the restaurant waiting for the rain to stop, patrons keep exiting the eatery and banging the door into them. About the fourth time this happens the door begins to open but as the shot cuts away briefly the viewer sees the door never fully opens and no one exits the restaurant. (A bit of rough editing.)
Continuity mistake: When Nadine is doing her 'Shakin' the Blues Away' song and dance she spins a number of times and by the end of the routine her hair has become quite undone in the front. As the audience applauds she disappears behind the stage curtain for just a second then reappears to take a bow. When she reappears her hair is perfectly coiffed.