When Maggie leaves the Professor's inner sanctum, she leaves her beret on a bust by the door. When Jo goes to leave, the bust and the hat are gone.
At the end of the film, Dick leaves an evening fashion show party to join Jo at the church for the final dance. But once the church scene begins, a hazy filter can't hide the fact that it was shot in broad daylight (complete with blue sky), even though it should still be evening.
When Dick leaves the first meeting with Duval to fetch Jo from the café, he says he will have her there at 10 o'clock the next morning. He later tells Jo that she needs to be there at 10:30, which would make her late twice in a row.
When the song "He Loves, She Loves" begins, Dick Avery puts his camera down on the grass. When Avery and Jo Stockton start dancing, the camera is missing.
When photographing in the book store, the assistant does not pull the dark slide far enough out of the 8 x 10 film holder to expose the entire sheet of film.
In the darkroom for the second print, a partly covered paper is exposed, but after developing a full format print is taken out of the bath.
In the darkroom scene, the print is left in the fixer for an insufficient amount of time; an experienced photographer, like Dick Avery is supposed to be, would not make this mistake.
At the beatnik club, the guitarist/singer's fingers don't always match the notes and strummed chords heard.
Fred's hair is a mess during the 'rings them bells' scene and he only corrects it when he gets to Flostre;s door.
After Dick kisses Jo and leaves the bookstore, Jo begins to sing "How Long Has This Been Going On". As she sings to herself while looking at the mirror in the supposedly empty bookstore, someone is reflected in the mirror moving around on the second floor of the bookstore.
During "How Long Has This Been Going On", when Jo is singing, a crew member can be seen in the mirror behind her.