From The Grindhouse Cinema Database
- Jennifer Connelly had part of her finger bitten off by the chimpanzee in the final scene at the end of the film. She was rushed to the hospital and the finger was re-attached.
- Director Dario Argento often cites this film as his personal favorite among his works.
- The film was inspired to Dario Argento after he learned that insects are sometimes used during murder investigations.
- Jennifer Connelly said in an interview that she was bitten by the chimp in this film. Apparently during one scene the chimp kept turning around and Dario Argento, not wanting to film her behind, asked Connelly to place her hand on the animal to stop her from turning. But when she attempted to do so, the chimp became enraged and bit her; and then became very hostile toward Connelly for the rest of the film.
- (at around 15 mins) The story Jennifer tells about her mother abandoning her was an actual story from Dario Argento's own childhood.
- A sequel to Phenomena (1985) was going to go into production in 2001 but it was canceled due to Dario Argento's contract with Medusa.
- The trained chimpanzee that plays Inga escaped into the woods at one point during shooting. After a few hours of searching she was found and returned to the set.
- Shot in English and dubbed into Italian.
- Most of the Italian and other non-English speaking actors/actresses actually dubbed their own voices into English for the USA and UK distribution.
- The shots of the swarm of insects covering the exterior of the school, and later nearly blotting out the moon were achieved through visual effects. They dumped a bunch of coffee grounds in a tank of water, filmed it, then superimposed the new footage over existing background shots.
- The larvae were created by placing vermiculite in water and adding liquid chocolate and essence of mint.
- The Patau Syndrome used in this movie is an actual syndrome, which is caused by a chromosomal abnormality.