All Men Are Perverts: In one episode the aliens are using a weapon that freezes time. Straker enters the film studio used to disguise SHADO headquarters and sees an actor permanently "glancing" down the cleavage of the well-endowed actress opposite him. Apparently even Straker is not immune — in "Close Up" he uses a sophisticated macroscope to look up the skirt of a posing Lieutenant Gay Ellis. Supposedly it's part of a demonstration on how it's impossible to judge magnification without reference points, but even after he gets the point Straker zooms in for a second look... you're not fooling anyone, you sly dog!
Artistic License - Physics: Contrary to what the writers of "Computer Affairs" seemed to think, there's no way a man could be shot from a submerged submarine into the air and not get the bends.
Auto Kitchen: In the first episode "Identified", the break room in Moonbase had what appeared to be an automat-style setup on one wall, with six different sets of slots divided by nationality.
Awesome Personnel Carrier: The fully-tracked Mobiles of SHADO have a radar dish on top and carry a squad of assault rifle-toting redshirts for taking on the anonymous alien invaders, yet are small enough to be deployed via aircraft.
Bait-and-Switch Gunshot: "ESP". While John Croxley is holding Ed Straker and Alec Freeman at gunpoint two shots ring out and Croxley crumples to the ground, dead. Paul Foster appears behind Croxley holding a gun - he heard Croxley threatening them and shot him to save their lives.
Big Brother Is Employing You: If two SHADO employees are having an affair, computer-psych tests are run to see if it will affect their performance. Straker wants to tell his wife the truth about his job, but it would put her life at risk from SHADO's own Security department.
Body Snatcher: After discovering a completely human 'alien', it's theorised that the aliens are Energy Beings who just use the bodies as hosts.
Brainwashed: A favourite tactic of the aliens, especially Manchurian Agent ("The Psychobombs", "Kill Straker!", "E.S.P", "The Cat With Ten Lives", "Destruction", "Mindbender" and "The Man Who Came Back"). "Timelash" is a notable exception, in that a voluntary traitor is used.
Subverted on Moonbase during normal operations: despite their Stripperific clothing, the female personnel run the base and command the male pilots.
...until a male main character turns up and takes over, and the trope is played straight again. This is partly justified because those men are higher in rank, but raises the questions why they have to micro-manage the women instead of letting them continue to do their jobs.
Catapult Nightmare: "Exposed". Paul Foster spots a UFO while piloting an experimental plane. Sky One destroys the UFO, but the explosion damages the plane and sends it into a dive. Paul Foster wakes up with a yell and sits up in a hospital bed, apparently after having a nightmare of the flight.
Comm Links: "Computer Affair". When a team of SHADO troops is sent in on foot to attack a UFO, the leader communicates with his superiors with a "wrist radio" version, complete with extendable antenna.
Compilation Movie: Several episodes were edited together in the late 1970's to make ''Invasion: UFO".
Concealing Canvas: "Exposed". Paul Foster breaks into the Ventura Aircraft Corporation to find evidence that he saw a UFO. He looks behind several paintings on a wall and eventually pulls one back, revealing a safe hidden behind it.
Da Chief: General Henderson of the International Astrophysical Committee, who's always going red in the face and shouting at Commander Straker, usually over SHADO's budget allocation. Ironically Henderson and Straker are quite friendly in the 'contemporary' scenes that take place before SHADO is operational.
Distant Prologue: Begins one year in the future (ie 1970) with Colonel Straker witnessing a UFO attack. The rest of the series takes place 11 years in the future (1980) when Straker is head of SHADO.
Enemy Mine: While shooting down an alien craft in one episode, Foster crashes on the Moon. His radio is broken, but he discovers that an alien is also alive (and his communications are also broken), and the two form a truce and co-operate to reach Moonbase. There's a hope that this show of good faith could lead to the alien entering Moonbase alive and opening negotiations with SHADO - but once they reach Moonbase, the guards think the the pilot is being held captive, and they shoot the alien.
Eureka Moment: "The Dalotek Affair". As part of one of their plots the aliens drop a meteor on the Moon. Late in the episode Commander Straker remembers a single word from a 10 year old TV broadcast ("fireball") and realizes that his subconscious mind is trying to tell him about the meteor's significance.
Everybody Smokes: Even on the Moonbase, medical areas, and computer rooms! Averted in "Sub Smash" where a nurse tells Commander Straker he can't smoke inside a hospital room.
Faceless Goons: In this case it's to enhance their mysterious and threatening nature, rather than so the audience won't identify with them. Though episodes where we're supposed to feel sympathy for a space-suited invader feature a lot more close-ups.
Flatline: In the episodes "Identified" and "Computer Affair" the death of a captured alien is graphically depicted by their pulses flattening out on a heart monitor machine.
Flashback Effects: "Court Martial". The teaser shows Colonel Foster being sentenced to death. The first act starts with a shimmering effect on the screen like falling water, then continues with the beginning of the events that led to the sentencing.
"Do you remember the Dalotek Affair, six months ago?" The Dalotek Affair...the Dalotek Affair...
Of course the real reason for disguising the base as a film studio was that the series was shot at a film studio! (Actually two in succession, because the first studio closed down during production.)
Future Music: "Ordeal" wrongly predicted that you can go to a party in the future dressed like Goldmember and not get laughed at; however it was correct in assuming that the Beatles song "Get Back" will still be popular.
He's Dead, Jim: Played straight in the episode "Sub Smash". After a Skydiver officer is injured during an attack he goes berserk and falls to the deck. Commander Straker (possibly) checks his pulse, puts his ear to the man's chest and says "He's out of it", meaning that he's dead.
It's Quiet... Too Quiet: "The Sound of Silence". Twice while near a lake a woman mentions that there's no sound from local animals. This is because there's a UFO hiding in the lake and a bodysnatching alien wandering around nearby.
It Works Better with Bullets: "Survival". While on the surface of the Moon, Paul Foster is captured by an alien. He manages to grab his gun back from the alien, only for the alien to open his hand to display the weapon's ammo clip.
Limited Wardrobe: A real-world example. They only had two alien uniforms, so there are never more than two aliens on screen at once. Also, there's a rather memorable red dress that shows up on several different female characters throughout the series.
In the first episode alone, there were three shots of female SHADO personnel in miniskirts or catsuits sauntering towards or away from the camera.
In the intro sequence, a curvy, catsuited woman is shown walking away from the viewer, the camera firmly focused on her behind.
The Men in Black: Though dressed a lot more stylishly. Well...colourfully anyway.
Military Mashup Machine: Skydiver, an atomic submarine with hydrofoil capability and a jet fighter attached to its nose. The name makes a lot of sense when you see the opening titles: "SKYDIVER" is written on the side of the hull. When the jet, "Sky One", separates from the sub, the word splits in two: the jet now says "SKY" and the sub "DIVER".
No New Fashions in the Future: In the 1980's wigs have replaced bad hairstyles, suits and ties have given way to turtlenecks and Nehru jackets, while catsuits and calf-boots are standard military uniform. Some of the civilian fashions aren't too different from the current fashion around 1970, while others are more on the bizarre side.
No Biochemical Barriers: The aliens can adapt human organs to replace their own, yet die if exposed to our atmosphere for too long.
No Pronunciation Guide: An idiosyncrasy of the series is that the term "UFO" is pronounced as a word ("you-foh"), as suggested by the real-world originator of the term Edward J. Ruppelt, and not as the more common "you-eff-oh". This is particularly true of the lead character, Ed Straker. Technically speaking the series title should properly be pronounced "you-foh" as well. However, the "you-foh" pronunciation was not consistently applied and some supporting characters use the now more common form.
Old-School Dogfight: Though special-effects limitations prevented much in the way of actual dog-fighting, the imagined space combat draws very much from Battle of Britain tropes. Moonbase is the beleaguered sector airfield, and SID (Space Intruder Detector) the early-warning radar. Calmly-speaking young women (the WAAF's) vector in Interceptors (Spitfires) against the anonymous alien invaders (German bombers). But given that the Moon takes 27.322 days to orbit the Earth, one wonders why the aliens don't just attack when Moonbase is on the opposite side of their target.
According to the numbers mentioned in the show, SHADO routinely tracks and attempts to intercept UFOs still flying faster than light. To have a prayer of doing this, the interceptors must be wicked fast for a sublight craft, enough for the relative position of the Moon not to matter much, I suppose.
Out of Order: Every TV broadcaster showed the 26 episodes in different order, due to the then highly-localized nature of the ITV "network" in Britain (this was completely normal at the time, and explains the absence of multi-episode plotlines) - in fact, three ITV regions once premiered different episodes of the show at the exact same time!
Rapid Aging: "Identified". After a UFO is shot down one of the aliens aboard it is captured. After he's exposed to the Earth's atmosphere he starts aging rapidly and quickly dies.
Red Alert: SID (Space Intruder Detector), SHADO Control and Moonbase all call them whenever a UFO is detected, so it happens on an average of once per episode.
Reentry Scare: "Kill Straker!" While a SHADO Moon ship is forced to re-enter the Earth's atmosphere at a steeper than normal angle a SHADO technician says "I have re-entry cessation on radio contact". The ship isn't found until 16 hours later, and Commander Straker comments on how worried he was.
Rewind, Replay, Repeat: "The Dalotek Affair". Straker catches a subliminal clue about UFO attacks from a documentary film, and insists on watching the clip over and over until he figures out what triggered the association.
"The Dalotek Affair" and "Ordeal". In both episodes Commander Straker says that aliens from another solar system came from a billion miles away, which would mean that they came from inside the solar system. The nearest star system to Earth is Proxima Centauri, approximately 4.24 light years or about 25 trillion miles away. Even if he had been using "billion" in the British sense, which is an American trillion, it still would have been wrong because a trillion miles is still much less than the necessary distance.
The way the moon-based spaceships are able to intercept UFOs coming from a totally different direction shows some lack of understanding of the distances involved.
Shoot the Dog: "A Question of Priorities", "The Responsibility Seat", "Ordeal"
Sigil Spam: SHADO puts its name and logo on all of its vehicles, even though SHADO's existence itself is secret.
This Page Will Self-Destruct: Straker is carrying a briefcase chained to his wrist with taped evidence of a Flying Saucer. When a British minister wants to look at the contents, Straker flicks a catch hidden under a nameplate, exposing the words DESTRUCT NEGATIVE, before opening the briefcase.
To the Batpole!: Pilots use chutes to quickly get to their interceptors on Moonbase and the SkyDiver submarine. SHADO's headquarters (hidden under a film studio) is accessed by Straker's office which serves as an elevator. As Gerry Anderson pointed out in a DVD Commentary, it's just as well no-one peeked into the boss' window and wondered why his office was sinking into the ground.
We Used to Be Friends: Straker thinks that Henderson should be in charge of SHADO; ten years later, they're constantly at each others throats.
When the Clock Strikes Twelve: "ESP". John Croxley's wife was killed by a UFO crashing into his house and he blames SHADO for her death. He lures Ed Straker and Alec Freeman to the ruins of his house with the intent of killing them at midnight.
Most of the "futuristic" fashions in the series seem very 1969-ish today. Even though most of the series was actually filmed in The Seventies, the design was probably done in the previous decade.
The turbine-powered, streamlined cars are obviously inspired by the concept cars of the 1960's.
The gender roles, with women mostly in subordinate jobs or as housewives, and lots of Bridge Bunnies around. Averted for the moonbase which has a female commander.
While not exactly outdated, the predictions of an extensive space/lunar industry and widespread use of supersonic transport already by 1980 feels like Apollo-era optimism today.
Averted in some cases: the series foresees the pervasive use (though not the nature) of computers in everyday life, spacecraft piggy-back launched from aircraft, voice print identification, car and cordless telephones, and that space debris will become a serious concern.