Trivia

According to Dr. Seuss, the film's creator and co-writer, one of the 150 boys vomited on the piano while filming. This caused a chain reaction and they were left with 150 vomiting boys. Seuss said later that the film's reviews were similar to this incident.

Marilyn Monroe accompanied young Tommy Rettig at the film's premiere.

The words Bart recites while making the blood oath with Mr. Zabladowski are taken word-for-word from the Scout Law of the Boy Scouts of America (trustworthy, loyal, helpful, friendly, etc.).

When Bart and Mr. Zadlabowski are taken to the dungeon via elevator, there is no reference to a third floor dungeon by the Elevator Operator. The third verse of the Elevator Operator's song was cut due to increasingly horrific lyrics referring to household appliances. The complete deleted verse went as follows: "Third floor dungeon, household appliances/Spiked beds, electric chairs/Gas chambers, roasting pots/And scalping devices." (the reference to "gas chambers" was probably regarded to be in bad taste since the film was made so soon after World War II and the Holocaust)

Allegedly, Dr. Seuss's first draft of the film's screenplay was 1,200 pages long. In this draft, Dr. Terwilliger (whose name was later changed to Terwilliker) kept Mrs. Collins locked in a cage that was suspended over his bed, where she endlessly recited rhymes declaring her loyalty to him, he had a magic saber that he used routinely cut off the heads of his incompetent henchmen, who then rose again from the dead and continued to serve him as headless zombies (albeit less efficiently without their heads), and in the finale, Bart Collins performed a song that encouraged the twins Johnson and Whitney to strangle him to death with their long Siamese beard, after which the other boys carried his dead body away.