David Croenenberg's The Fly is about a scientist's experiment that goes horribly wrong.
*Several sequences were filmed but cut from the final release, including: a sequence where Brundle sends a cat and the surviving baboon through the telepods, resulting in a mutated creature he beats to death with a pipe; a scene where Brundle climbs the outside of his building as an insect limb emerges from his side; and an alternate ending in which Veronica has another dream of her unborn child, this time as a baby with beautiful butterfly wings.
*It took nearly five hours to apply the most extensive makeup stages to actor Jeff Goldblum.
*The Chris Walas, Inc. designers studied graphic books on disease as a starting point for their "Brundlefly" makeup/creature designs. The final "Brundlefly" creature is horribly deformed and asymmetrical. This reflects director David Cronenberg's idea that the creature shouldn't be a giant fly, but rather a literal fusion of a man and an insect that embodies elements of both.
*Originally a project for Tim Burton to direct.
*The line, "I'm saying I'm an insect who dreamt he was a man and loved it, but now that dream is over and the insect is awake," is a reference to author Franz Kafka's 1912 story "The Metamorphosis," in which a man wakes from a nightmare to find himself transformed into a giant insect.
*Scripted, but never filmed, was a segment meant to have followed the deleted monkey-cat scene: A homeless lady screams after interrupting Brundlefly as he feeds out of an open dumpster. Brundlefly seizes the bag lady and disintegrates her face with his vomit drop. Before he finishes feeding on the woman's corpse, Brundlefly's humanity emerges for a moment; just long enough to contemplate the horror of his sub-human existence.