"The Invisible" is based on the Swedish film "Den Osynlige" (The Invisible (2002)), which was very loosely inspired by a novel of the same name by the Swedish writer Mats Wahl.
The last film to be released by Hollywood Pictures before the label was completely dissolved by Disney.
A subplot was removed involving drug smugglers. It was feared this would give it an R-rating and wasn't necessary to the plot.
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.
When the researcher looks through Nicks room the day after the party, a copy of the book Catch-22 is seen on the bookshelf. The whole movie plot is about a Catch-22.