Acting for Two: Paul Stassino plays both Francois and Angelo since Palazzi's real face and voice are never heard or seen.
Cast the Expert: The B-17 that picks up Bond and Domino at the end of the film was owned by a CIA front company and its Skyhook system was actually used in real life on at least one espionage mission - Project COLDFEET.
Cast the Runner-Up: Luciana Paluzzi auditioned for Domino, but decided it would be more fun to play a bad girl.
Enforced Method Acting: Sean Connery and the sharks in Largo's pool. The clear plastic panels that shielded Sean Connery from the sharks could only extended about three feet in height and sharks could swim over them. Some sharks did and Sean Connery was genuinely terrified. Guess which takes the director used in the film?
A justified example, with the decision to change Largo's death from a gruesome harpoon through the neck, to a relatively more tame but more dramatic harpoon through the back.
The producers deciding at the last moment to require the theme song to have the word "Thunderball" in it, necessitating some quick rerecording and quick rescoring to fit the new song in.
Fake Nationality: George Pravda, who played a Polish scientist, was Czechoslovakian.
Looping Lines: Q introduces Bond to his new tricked-out briefcase, accompanied by the line "Now pay attention, 007". This line would later become one of many famous motifs in the series, but Desmond Llewelyn does not move his mouth.
The Other Darrin: Felix Leiter is recast yet again, this time with Rik Van Nutter, apparently doing his best Jack Lord impression, with Leiter once again being depicted as a young man after the previous film had him grey-haired and middle-aged. Possibly happened with the voice of Blofeld as well, as various sources claim that Joseph Wiseman (the titular Dr. No) took over the role from previous actor Eric Pohlmann in this film, while yet others say that it was still Pohlmann.
Real Life Writes the Plot: James Bond takes a moment to don a helmet before flying off in the jetpack because the stunt pilot absolutely refused to perform if the producers wouldn't consider his safety.
It was originally thought that the title would be too awkward to work into a song, so instead Barry and lyricist Leslie Bricusse wrote one for Dionne Warwick called "Mr. Kiss Kiss Bang Bang." This is why the club Bond runs into to escape Fiona's goons is called The Kiss Kiss Club. The decision to replace it with the Tom Jones song was made relatively late in the production which is why the melody for "Mr. Kiss Kiss Bang Bang" is still part of the soundtrack.
The original draft scripts did not involve SPECTRE, but Italian mobsters in the Sicilian Mafia, with Largo as a crime boss. This was the reason why many of the villains were played by Italian actors.
Rik Van Nutter had a contract to appear as Felix Leiter in the next several Bond films, but they couldn't figure a way to work the character into either of the next two (Leiter did not appear in either original novel).
The opening sequence, in earlier versions of the script, was set in Hong Kong at a fan-tan parlor strip joint. The man in drag story element, was still the same though. He was dressed in a peacock outfit, and sat in a gold cage.
Bouvoir was originally to be strangled with his own bra, rather than the poker that was eventually used.
The original climax was much different - Having been rescued from the underwater cave, Bond joins Leiter on a hovercraft and they team up with the aquaparas for the final battle as SPECTRE try to drop the first bomb in a sunken wreck. Largo escapes to the 'Disco Volante', but before it leaves Bond gets on board. Largo is killed by Domino, and Bond and Domino jump to safety from the hydrofoil which is now out of control. Kutze is left on board and destroys the ship by detonating the fuel tanks. After Domino and Bond are picked up by Leiter in the hovercraft, there is a final scene shown as the credits roll: the ransom is dropped by an air force plane and the package sinks to the sea bed where it is intercepted by a two man SPECTRE sub. As the mechanical arm extends to grab the package, it explodes.
Originally, Bond and Pinder were to have descended on 'Palmyra' for the night sortie. They were to have gone to a boathouse, to see what had made two tracks in the sand. They find it is just a pedalo, but accidentally set off the alarm, and in the following gun battle on the beach, Pinder is killed. The scene would have ended in the same way as the film, with Bond jumping free of the shark pool - although the line he was to have said was: 'Sorry you'll have to order something else.'
Originally, Bond was to escape from Volpe, after bedding her, by escaping down his hotel corridor, dressed in costume for the Junkanoo. He was to pick up a cookstove from a nearby waiters trolley and use this is as a weapon, although Volpe did manage to get a shot at him - which would have led into the Junkanoo sequence.
When Bond and Domino meet underwater and disappear behind a rock, the scene was originally supposed to show Domino's bikini float out from behind the rock. Albert R. Broccoli vetoed this, because he felt it was too suggestive.
Adjusted for inflation, Thunderball is the second most successful Bond movie after Skyfall. Its adjusted figure is over $950 million. On US and Canadian grosses alone, it is, according to Wikipedia, the 30th highest grosser of all time, beating all of the Harry Potter movies (the "Potter grosses more than Bond" figure is inaccurate, since it doesn't adjust for inflation) and every one of the The Lord of the Rings movies.
Trivia tropes for the novel:
Reality Subtext: Bond's medical record, as read out to him by M, is a slightly modified version of Fleming's own.
What Could Have Been: Kevin McClory planned to have a third adaptation of the book made for 1995, possibly under the title Warhead or Warhead 2000.
Write What You Know: The visit to the health clinic was inspired by Fleming's own 1955 trip to the Enton Hall health farm.