The rats that Danton eats were purchased at a pet store.
The 35mm film stock used to film the movie was Short Ends. All AIP movies used short ends (of film) as their film stock. This is a term given to left-over film from better budgeted films which can be bought at a cheaper price. The largest (longest) rolls were saved for dialogue and short rolls were used for action scenes, which meant the camera was constantly reloaded with new film on every take. Numerous emulsion batches were used which meant every roll was different and the rolls were different ages - some were old.
There was no time spent color-timing in post-production. There was an aim to not use different stock types in the same scene (eg. 100asa, 500asa, Fuji, Kodak and AGFA). Because of this, there has been some speculation that the movie was filmed on 16mm, however it was 35mm short ends.
In May 2020, this film aired on German TV station Tele5 as part of the "SchleFaZ" series.