Ass Pull: Q never once explains to Bond that the infra-red underwater camera has a built-in Geiger counter (only that the watch does) which comes as something of a surprise when Domino uses it later on in the film. (In the commentary, actor Desmond Llewelyn complained that his favorite part of the Q scene ended up on the cutting-room floor; perhaps the explanation was part of that bit.) This is an adaption-induced mistake, as the book version of the device had the Geiger counter in the camera and a measuring dial on the watch connected by a thin wire up Bond's sleeve.
Awesome Music: Probably the only Bond film to have had four songs recorded.
Shirley Bassey was the first to record a theme, after the success of Goldfinger, and called "Mr Kiss Kiss Bang Bang". An instrumental version of "Mr. Kiss Kiss Bang Bang" is heard at various points during the movie as a kind of secondary leitmotif. After some apparent problems with Bassey's singing, Dionne Warwick was brought in to do another take of the same song. The producers planned to use the Warwick version of "Mr Kiss Kiss Bang Bang" over the end credits, until Shirley Bassey sued. The Warwick version of "Mr Kiss Kiss Bang Bang" is featured in its entirety on the secondary commentary track of the Thunderball laserdisc/DVD/Blu-ray.
The one they eventually went with was Tom Jones' iconic "SO HE STRIKES! Like thunderball..." track. The film was set to go with Warwick's version "Mr Kiss Kiss Bang Bang", but at the last minute the producers insisted that, no, the theme had to have the word "Thunderball" in it, so a new song was hastily written to be recorded by Tom Jones and parts of the film were rescored to feature the instrumental version of that song as a leitmotif too. Tom Jones actually passed out after holding that really long note at the end.
Johnny Cash (of all people) also recorded a song, also called "Thunderball", and submitted it to the EON producers. Unsurprisingly, it sounded too like a western for a Bond film. Still, sometimes one likes to imagine that in a Alternate Universe Cash's music is the theme for a Wild Wild West movie starring Robert Conrad and Ross Martin...
Bond clobbering the SPECTRE agent in the opening is a well-staged and hard-hitting fight scene, but it's undermined by the fact that the SPECTRE agent is in drag.
Bond on the overcranked stretching machine Death Trap is supposed to be something that has the audience on the edge of their seats, but it just looks ridiculous. Quite frankly, he looks like he's humping the table.
The name "Disco Volante". Yes, it means "Flying Saucer" in Italian, but "disco" has other connotations nowadays.
One-Scene Wonder: Patricia Fearing the nurse, especially when she's out of uniform and being massaged. This is true on a larger level, too. Due to a dispute with her agent, Fearing's actress Molly Peters was unable to follow up on the career bump even one-scene Bond girls usually got—she never landed another major film role. An unfortunate waste of such a lovely actress.
"Seinfeld" Is Unfunny: The plot using a nuclear weapon to extort a ransom was considered a unique idea when this film came out. Now it's become one of the most cliched Evil Plans in the book.
So Okay, It's Average: While it was a huge box-office success on its initial release, in retrospect it's probably the least discussed film from Sean Connery's run in the role. Whereas the previous three films are seen as all-time classics, You Only Live Twice silly but iconic, and Diamonds Are Forever the first serious misfire in the series, this one's generally only remembered for the controversy behind the scenes (which led to the subsequent creation of Never Say Never Again), as well as the title sequence and Tom Jones's theme song, both of which are considered strong contenders for the best in the series.
Tough Act to Follow: Thunderball is still well-regarded in its own right. However, it usually isn't considered as good as its predecessor either, especially since the latter film is one of the biggest contenders for best in the series.
Bond blackmails a civilian woman into sleeping with him. The best you can say is he didn't intend to do it, but he's quite willing to take advantage of her misconception. The fact that she's wearing a big goofy grin indicates she's deliberately Playing Hard to Get, but that doesn't make it much less creepy. Plus, the cold open has the Creepy Crossdresser give himself away because there's no way a woman would ever open a car door for herself.
Even worse in that the book simply had Bond flirt with Fearing, agree on a date, and do it consensually later on.
These days the filmmakers would never get away with harpooning a real, live shark on-screen.
Visual Effects of Awesome: The underwater scenes in this movie are revolutionary for the time period, but what's truly impressive is how well they've aged. Most of the underwater sequences, especially the war at the end, still look downright beautiful today.
Overshadowed by Controversy: Whenever you hear people discussing Thunderball, it's usually less about the merits of the novel and more about the intense copyright infringement fiasco between Ian Fleming and Kevin McClory, who claims credit for the novel's conceptualization.
Bond is impressed by Domino, because she "drives like a man". (In the movie, he says she "swims like a man.")
Fleming also goes on a very clear Author Tract about how having four women in a car is bound to cause terrible accidents because the driver will turn around to chat with her friends and probably cause a car crash.