Originally, it was to be established Bond had plastic surgery done to explain why he doesn't look like Sean Connery anymore. And other movies establish that Blofeld is constantly changing his appearance.
Bond is trapped in the ice-skating rink while SPECTRE mooks search through the crowd. Bond is in despair, expecting to be captured again when suddenly Tracy (whom he last saw in Portugal) appears in front of him, with an ice-modified fast car to get Bond the hell out of there. An impressive achievement for a Bond girl!
Bond One-Liner: Bond gets a particularly brutal one when a mook falls into a large snowblower and gets cut to pieces by it:
"He had lots of guts!"
Interestingly, Bond sends a one-liner Blofeld's way after the bobsled scene only to find out later that he wasn't dead (unfortunately it was probably the worst way possible).
Justified as Blofeld wants the governments to give him a pardon so he can become a Karma Houdini. Killing Bond would just make things more tense.
Book Ends: Bond and his Aston Martin in Portugal driving down the same road, stopping the car each time for Tracy. The first time, he stops the car to save her from drowning. The second time, they're married, discussing their future when she's shot to death.
Musically, the beginning of the film when Bond saves Tracy and the end where Bond pursues Blofeld both use similar musical motifs (on the OST, the first track is called "This Never Happened to the Other Fella", while the latter track is called "Bobsled Chase").
Brainwashed: Blofeld's latest scheme involves turning young women into unwitting bioterrorists.
Call Back: References to Bond's dead wife were made repeatedly in other movies, often cutting off before saying what happened to her; since OHMSS is slightly obscure, quite a lot of people do not know that we actually saw what happened.
The cheerful "Do You Know How Christmas Trees Are Grown" reappears during Bond's Cable-Car Action Sequence as a more suspenseful tune, see below.
Distracted by the Sexy: When Tracy recognises her father's voice on the radio from the approaching "Red Cross" helicopters, she immediately starts being nice to Blofeld, who gets annoyed when one of his men tries to draw his attention to them.
Drugs Are Bad: Marc-Ange Draco, head of the Unione Corse, the biggest European crime syndicate, commits murders, extortion, theft, sexual slavery, and many, many other crimes. But he's a good guy because he doesn't sell drugs.
Epic Movie: This is one of the most sprawling and operatic of the Bond films.
Even Evil Has Standards: Marc-Ange Draco, head of the Unione Corse, the biggest European crime syndicate (and Tracy's father), agrees to to assist Bond and the entire British Government against the efforts of SPECTRE to gain Bond's help with his daughter. Later, he personally leads an invasion of Blofeld's fortress to rescue Tracy and stop Blofeld's plan to destroy the world's food supply.
Meta example: The whole resignation from Her Majesty's Secret Service business would mirror Lazenby's decision to quit the series.
In the novel, the recently engaged Bond has a slice of Christmas pudding with trinkets baked into it at a party, and his slice has the bachelor's button in it, implying that he won't be married for very long.
Karma Houdini: Irma Bunt is the person who actually kills Tracy and she is never seen again in this or any other Bond film, which means that the murderer of Bond's wife got away with it completely. A case of Real Life Writes the Plot, the actress Ilse Steppat died mere days after the film's release. The comics ultimately rectified this, by having her show up again and be killed off.
MacGyvering: Bond does this at least twice at Piz Gloria.
He uses a document clip, an eraser folded in half and the brass edge from a ruler to open his electric room door.
Later, one of Blofeld's patients used a emery board (non-metallic nail file) to sneak into his room.
After his cover was blown and he was locked up in a machine room, he pulls out his pant pockets, tearing them off to improvise a pair of gloves that would allow him to grip the cable car lines, aiding in his escape.
Mood Whiplash: The last ten minutes. Made more jarring by the soundtrack, which changes abruptly from a sad reprise of "We Have All The Time in the World" to a loud, brassy version of "The James Bond Theme".
He doesn't actually fall for Tracy until after that. And he doesn't really know they are being brainwashed, though obviously he's suspicious of the (voluntary) hypnotism, which he only finds out about after he starts sleeping with them. And being Bond, it was obviously too late by then.
Also, the hypnotism might not have affected that part of their personality.
One other explanation: Bond sleeping with the girls is in the line of duty, something that has to be done to complete his mission. With Tracy, he's clearly in love.
No-One Could Have Survived That: Blofeld gets his neck tangled in a branch at 45 mph, complete with a shot of his lifeless legs dangling in mid-air (bringing an execution to mind). He later reappears in a neck brace. Oops.
Oh Crap: During the final bobsled chase, Blofeld drops an active grenade intended for Bond and desperately struggles to get it out. He barely manages to grab it and toss it out in time.
Bond, when Irma Bunt catches on to him and his escapades.
Ominous Music Box Tune: The first few notes of "Do You Know Where Christmas Trees are Grown" (a cheerful song that played in the background earlier) can be heard in a tense scene after 007 is locked in a cable car machine room. It foreshadows Blofeld's gift of a music box to the girls.
A rendition of the Bond theme's melody is played by an eerie synthesized music box during the gun barrel sequence.
Irma Bunt was Ilse Steppat's only English language role. She died shortly after the film came out.
Peter Hunt quit the franchise after this film. He'd been the editor for the first four films and had a falling out with Broccoli and Salzman over being passed over for directing You Only Live Twice. That and the problems shooting this film figured in his decision.
Lazenby's story is well-known.
Only One Name: Fräulein Bunt refuses to let the patients reveal their full names, claiming clinic rules. Ruby Bartlett tells "Hilly" her name anyway when they're alone.
Real Men Dont Cry: Bond is perfectly — indeed, creepily — calm in the final frame. Lazenby wanted to do some real emotional acting, but the director insisted that Bond, a trained killer, is basically dead inside and can't shed a tear even if he wishes.
Though if you listen carefully, when Bond turns away and holds Tracy's body close, you can hear him softly weeping just before the "The End" appears on the screen.
Redundant Rescue: She still needs help to get out of the complex, but when the Big Damn Heroes arrive at the end Tracy has killed the man guarding her and just needs a ride home
Refuge in Audacity: The basic plot of holding the world hostage with a sterility virus is sound (and, for its time, quite original), but brainwashing a cadre of international beauties so that they will unleash the viruses by radio-induced hypnotic command, is just a tad over the top, don't you think?
Title Montage: Various clips from the five previous Bond movies can be seen during the intro sequence.
Took a Level in Badass: Perhaps in light of Telly Savalas' previous experience in action and war films Blofeld, as played by him, is shown less as the seated, cat-stroking Smug Snake as in previous (and later) films. Here he's a brute, plain and simple. He is shown on skis chasing Bond himself once he escapes from the Piz Gloria, setting off an avalanche, and being pretty much an expert bobsledder.
Arguably, Bond is more willing to put up a fight than before.
Each of Blofeld's "patients" could only eat one and only one kind of food as part of their treatment: chicken for Ruby; flatbread for the Indian girl, bananas for the Jamaican girl which she ate seductively; and so on.