Continuity: During the lively dance at the library, Marian backs up into Prof. Hill's leg twice.
Continuity: During the "Shipoopi" number, Marcellus Washburn gives his hat to the little boy twice.
Errors in geography: In the widescreen version, the power-towers and electrical wires in the Hollywood Hills behind the Warner Bros. backlot are plainly visible as Hill walks from the train depot into River City.
Crew or equipment visible: Lights and camera equipment seen in the store windows during the "Wells Fargo Wagon" song number.
Continuity: At the end of the Wells Fargo Wagon song, while Mayor Shinn is waiting for Marian to give him the education journal, Marian opens the book twice.
Continuity: In the candy shop scene where Marian and Hill are sipping soda, Marian reaches into her purse twice.
Revealing mistakes: In the closing credits, when Susan Luckey and 'Timmy Everett (I)' have their moment while marching down the street, she nearly knocks off his tall hat with her baton, apologizing on camera.
Anachronisms: From the fashions, the cars, the mention of Harold Hill being a member of the "Class of 1905" and general tone, the play/movie would appear to take place around 1910. However, the mentioned "Cap't Billy's Whiz-Bang" did not begin publishing until 1919. "Whiz-Bang" was published by a World War I veteran, and comes from the dough-boy's name for a type of artillery round.
Anachronisms: This story takes place in 1912 - the adoption of the 48-star US flag is mentioned. At the climactic scene in the town's school, when the boys' band plays the Minuet of Beethoven, we see the state flag of Iowa, a flag that was not adopted until 1921.
Continuity: Chairs in front of the stage move around during the July 4th celebration in the auditorium. First there are three together with one chair a ways off to the left; then later, as one of the school board members prepares to sit down, the four chairs are in a group.
Continuity: Harold leaves Tommy to direct the band and goes to the Candy Kitchen, but sitting at the table is Tommy and Zaneeta.
Anachronisms: The movie is set in 1912, but the musical number 'Trouble' mentions the beverage Bevo which was not manufactured before 1916.
Anachronisms: Hill asks the townsfolk during the "Trouble" number: "Wanna see some stuck-up jockey boy sitting on Dan Patch?", indicating that Dan Patch, a champion harness racing horse, was still active when the story takes place in 1912. However, he was retired in 1910.
Continuity: The final parade sequence is filmed on both sunny and overcast days.
Continuity: In the number Marian the Librarian, Harold runs off-screen, but on the next scene he is seen sitting where he ran off from.
Revealing mistakes: As Hill is getting onto the train at the beginning of the movie, it can be seen that the train's wheels are just painted on.