It was reported at the time that George Lazenby and Diana Rigg didn't get on. While they weren't exactly friends, they had their good days and bad days. The rumours started when it was reported that Rigg ate garlic before a love scene (which wasn't true - she said to Lazenby as a joke that she was having garlic for lunch). She later admitted that she found Lazenby immature. Lazenby for his part claimed that he got on with everybody - except director Peter R. Hunt. He claimed that he didn't receive any coaching despite his inexperience and that Hunt asked the rest of the crew to keep a distance from him, as "Peter thought the more I was alone, the better I would be as James Bond."
One time, we were on location at an ice rink and Diana and Peter were drinking champagne inside. Of course I wasn't invited as Peter was there. I could see them through the window, but the crew were all outside stomping around on the ice trying to keep warm. So, when she got in the car, I went for her. She couldn't drive the car properly and I got in to her about her drinking and things like that. Then she jumped out and started shouting 'he's attacking me in the car!' I called her a so-and-so for not considering the crew who were freezing their butts off outside. And it wasn't that at all in the end, as she was sick that night, and I was at fault for getting in to her about it. I think everyone gets upset at one time.
Lazenby overall was reported to be quite a prima donna on the set, sure that he would become just as big a star as Connery with the role. This probably contributed to his not doing any more Bond films. He later went on record as saying that it was mainly him listening to very bad advice by his agent that made him behave that way, including his decision to stop making Bond films. The fact he always said in later interviews that this was one of the worst decisions he ever made but that he also fired his agent just a couple of years later really does not come as a surprise if this in fact is true.
Magnum Opus Dissonance: Despite being one of the most obscure Bond films amongst the general populace, often inaccurately thought to be a financial failure, the producers and EON have gone on the record saying that if they had to choose one Bond movie to preserve for future generations, it would be OHMSS.
No Stunt Double: Blofeld getting snared with a tree was performed at the studio by Telly Savalas himself, after the attempt to do this by the stuntman on location came out wrong.
Irma Bunt was Ilse Steppat's only English language role. She died shortly after the film came out.
Peter Hunt drifted away from the franchise after this film. In an interview, he explained that Broccoli and Saltzman asked him to return for Diamonds Are Forever and subsequent films, but he was always busy with other projects at the time and sooner or later they stopped asking.
Telly Savalas replaced Donald Pleasence as Blofeld. This is a holdover from the original book, where Blofeld had plastic surgery to alter his appearance to make him harder to identify. It still doesn't explain why he fails to recognize Bond.
Bond's sliding along the ice whilst firing a machine gun in the attack on Piz Gloria was a spur-of-the-moment idea from director Peter R. Hunt.
The St. Bernard rolling in front of Bond was totally unexpected, and Lazenby reacted accordingly ("Never mind that! Go and get the brandy, huh?").
Troubled Production: The film had a few stuntmen accidents (including one guy losing a foot), and leading man George Lazenby had conflicts with the director and the producers. On top of that, the press had a field day with the production and created huge stories out of the most innocuous events; lead actress Diana Rigg's off-hand quip about eating garlic prior to a scene resulted in stories that the two leads could barely even stand to work together (which, to be fair, wasn't completely untrue), while the news that George Baker would be overdubbing some of Lazenby's lines — specifically the ones where Bond was impersonating Baker's character, Sir Hillary Bray — ended up being interpreted as Lazenby having proven to be such a terrible actor that the producers had been forced to have Baker overdub his entire performance. These stories naturally made the already-strained mood on the set even worse, and played a part in Lazenby's decision not to return to the role.
The role of Bond was offered to Timothy Dalton, who declined because he felt at 23, he was too young and inexperienced. He also didn't want to take over from Connery.
Adam West, a personal friend of Albert R. Broccoli, was offered the part of James Bond for the movie. West said that while he was very tempted, he ultimately turned it down feeling the role should be played by an English Actor.
Cubby Broccoli offered Jeremy Brett the role of 007 after seeing him in My Fair Lady. Brett ultimately declined the role, saying - "It's the sort of role you cannot afford to turn down, but I think it would have spoiled my life if I had got it."
In the commentary, George Baker (Sir Hillary Bray) explains that Ian Fleming had put him forward as his choice to play James Bond when he was trying to drum up interest for a film series, before Saltzman and Broccoli got involved. In that light, Baker noted it gave him an odd feeling to be in the studio dubbing Lazenby's dialogue for when Bond was impersonating Bray.
Had George Lazenby's agent not convinced him to leave the series, his contract was for seven movies. Tracy's death would only occur in the follow-up, but since the main actor was leaving, the producers decided to keep it in just one movie—and Bond seeking revenge for Tracy's death was not (explicitly) addressed within the franchise until For Your Eyes Only. note Bond is on a Roaring Rampage of Revenge against Blofeld in Diamonds Are Forever, but it is left deliberately ambiguous if this has anything to do with Tracy or if this movie was being skipped; his behaviour makes sense either way however.
Irma Bunt was supposed to come back in the next film (likely for Bond to get a proper revenge on her), but Ilse Steppat died of a heart attack only four days after the international release of OHMSS, hence the Karma Houdini.
In order to explain why Bond looks different, the original script explained that he had plastic surgery because he kept getting recognised by all his enemies. This was scrapped because they realised it was a terrible idea, dodging a continuity bullet when Connery later returned to the role; a continuity error, however is created as Blofeld fails to recognize Bond, despite the two having met face to face in the preceding film.
An entire action scene was cut due to time. Bond was originally supposed to catch one of Blofeld's henchmen spying on his meeting with Sir Hilary and give chase across the rooftops of London.
Lazenby suggested a scene where Bond skis off a cliff and opens a parachute. This was scrapped, as the filmmakers lacked the resources to pull it off. It was used as the opening for The Spy Who Loved Me.
Lyrics were originally intended for John Barry's main theme, but were later rejected in favor of "We Have All the Time in the World".