Don Hertzfeldt single-handedly animated and photographed tens of thousands of drawings for the film, over the course of four years.
Over 60 actors recorded vocal performances for over 150 individual animated human characters. These intense first three minutes of the film alone - "the crowd scenes" - took around two years to complete.
Over 45 minutes of footage was reportedly photographed for the film's final 12 minute running time. This is an enormous shooting ratio for any animated film, due to the unprecedented amount of special effects and experimental lighting techniques that required multiple takes.
All special effects were done "in camera", no CGI was used in the production of this film.
Many of the film's complicated animation and visual effect sequences required several months of work just to produce a few second's worth of finished screen time.