"The Invisible" is based on the Swedish film Den osynlige (2002), which was very loosely inspired by a novel of the same name by the Swedish writer Mats Wahl.
A subplot was removed involving drug smugglers. It was feared this would give it an R-rating and wasn't necessary to the plot.
WILHELM SCREAM: About 25 minutes into the movie, when a guy gets thrown into a swimming pool.
The shirt that Nick is wearing at the end of the movie bears a crow on the chest. In some Native American legends (and the graphic novel by James O'Barr bearing the name) the crow could carry a person's soul back from the land of the dead.