Trivia

Alejandro Amenábar imagined the script after having horrible nightmares while ill with the flu.

Tom Cruise said that he was on his mobile phone trying to buy the remake rights during the end credits the first time he saw the film.

Penélope Cruz also stars in Vanilla Sky (2001), Cameron Crowe's remake of this film, playing the same character, Sofia.

César's apartment uses same set used by the character of David in Pedro Almodóvar's movie Live Flesh (1997), which also starred Penélope Cruz.

Included among the "1001 Movies You Must See Before You Die", edited by Steven Schneider.

Alejandro Amenábar: with other two people in the bathroom of the disco, when César goes there. He is the last one that gets out.