The character's name "Michael Griffin" is a direct reference to the character of "Griffin" from H.G. Wells' 1897 serial novel "The Invisible Man". In Wells' story, Griffin was driven insane by his invisibility - much like the character in this movie.
(at around 45 mins) The flashback scene in which Christian Slater is becoming invisible re-uses footage from the original El hombre sin sombra (2000).
(at around 36 mins) The prescription bottle Frank Turner places on Detective Harrison's desk is labeled "Kindasortacyn" and its generic equivalent, "Somethinesleacyn".
There were only 250 visual effects shots in the whole film, and 80 of them were simply wire removals.
Paul Verhoeven: (at around 1h 1 min) The newspaper photo of one of the killed people is of the director of the first El hombre sin sombra (2000). The photo was taken on location while filming Starship Troopers (Las brigadas del espacio) (1997), but has been altered for its use in this film.