Kubrick was on welfare during the making of this film.
Working with practically no budget and largely without on-location filming permits, Stanley Kubrick had to remain unnoticed while shooting in the nation's busiest city, sometimes secretly shooting from a nearby vehicle.
Kubrick uses a brief shot of a negative image during Davey's nightmare, which instantly evinces scenes from 2001: A Space Odyssey (1968).
Unable to record the film's dialogue on-set due to technical problems, Stanley Kubrick was forced to post-sync all of this film's dialogue and sound effects.
Veteran soundman Nathan Boxer was hired to record sound. However, after his boom mike and pole created many shadows, the inexperienced Kubrick was forced to fire him and his sound crew. Irene Kane was unavailable to add her dialogue later, so the voice of another actress was used.