Trivia: Victoria Tennant hated the scene where her character was to be killed off so much that she refused to film it and walked off the set. The scene then had to be done by a stunt double.
Trivia: During filming, Val Kilmer became so difficult to work with, that after his final scene was filmed, director John Frankenheimer ordered his crew to "get that bastard off my set."
Trivia: Julie Delpy admitted that the only reason that she did this movie was because she needed to pay her rent.
Trivia: John's request for "guns...lots of guns" mirrors a line Keanu Reeves has in The Matrix.
Trivia: Laurence Mason's character Lord Nikon was given the name because of his photographic memory.
Trivia: When Ace enters the club to meet the guy with long blond hair and glasses, the song playing is "Hammer Smashed Face" by death metal band Cannibal Corpse. Jim Carrey is a fan of Cannibal Corpse and insisted they appear in the movie since it takes place in Florida, the "capital" of death metal.
Trivia: Mark Knopfler, who composed the music to the Princess Bride, only agreed to do so if Rob Reiner could include the baseball cap he wore in the film Spinal Tap. The director placed the cap in the boy's bedroom, beside the bed.
Trivia: The Sator Square dates back to Pompeii and is a square of 5 Latin words making a palindrome: Sator, Arepo, Tenet, Opera, and Rotas. Whichever orientation the square is in the words line up in both directions. Each word features in the film - Kenneth Branagh's character is named Sator, the forger mentioned near the start is Arepo, the title is of course Tenet, the opening sequence takes place in an Opera, and the Ukranian special forces who arrive in that sequence have badges on their arms with "Rotas" on them.
Trivia: Screenwriter Aaron Sorkin has a cameo as a lawyer in a bar talking to a woman about one of his cases.
Trivia: The infected identify each other and the uninfected by sense of smell.
Trivia: The TV edit of the film differs widely from the theatrical release - lots of footage was purposely edited out, such as when the dead Norwegian on the table blinks, and there is also a narration. Director John Carpenter has publicly stated that he finds the TV edit embarrassing and a disgrace to his movie.
Trivia: The Terror Incognita roller coaster is actually The Hulk roller coaster in Universal Studios, Orlando.
Trivia: During the big chase scene Marilyn Burns was running so slowly that Gunnar Hansen stopped to cut tree branches so he wouldn't outrun her.
Trivia: Jesse Ventura was delighted to find out from the wardrobe department that his arms were 1" bigger than Arnold Schwarzenegger's. He suggested to Schwarzenegger that they measure arms, with the winner getting a bottle of champagne. Ventura lost because Schwarzenegger had told the wardrobe department to tell Ventura that his arms were bigger.
Trivia: The big fight scene is spoofed in "South Park" when the crippled kids Timmy and Jimmy fight, instead of the film's Nada and Frank. The episode is called "Cripple Fight".