Sometimes, in combat, it's hard to tell who your friends are. Amidst the smoke and confusion in a battle, allied units may get lost and not be where they planned to be. Other allied units on the move may misread their maps or call in wrong firing coordinates. Or a tank crew or antiaircraft battery may misidentify an approaching allied vehicle as an enemy.
In a combat zone, firing on, questioning, or fleeing your friends is common. With Due Respect may not be very respectful, as the junior cannot tell whether the character speaking to him actually is his senior officer.
Confusion deliberately induced by the villain is Let's You and Him Fight. Dressing as the Enemy can also lead to this, as can catching someone unawares (this sort of confusion can also be induced via Disguised Hostage Gambit). Unfriendly Fire often relies on this to cover up the murder. Extreme forms of Divided We Fall can lead to this. The Berserker often does not care which he's attacking, or is too caught up in the rage of battle to tell them apart. Can apply even if one character does know who is there, but has been lied to about his character, which often leads to the problems of Would Not Shoot a Good Guy.
This is often even worse before or after the actual fighting, while you are sneaking about territory that you know that the enemy is about somewhere, or into his stronghold, especially if you are a prisoner or trying to contact one. (See Alone-with-Prisoner Ploy.)
Note that the characters do not have to be in doubt ― they can just be wrong. They may (briefly) believe the approaching forces to be friendly, or they may go through all sorts of fighting and fleeing believing them to be foes. Get It Over With often reveals this trope was in play.
Truth in Television. In Real Life, 'friendly fire' (AKA "blue-on-blue engagement" among NATO forces, fratricide, or "own goal" as the Brits call it) has been a serious issue in many conflicts. This problem goes far enough back that it's responsible for battle cries, military uniforms, battle standards, and heraldry. Books have been written about the resulting investigations. Armies have developed many innovative designs to avoid it, but have never been 100% successful — partly because if you can always identify your friends, so can your enemies.
Contrast with Friendly Fireproof, where you can hammer away at your teammates and not cause any damage at all.
- In Code Geass, Lelouch uses the enemy's Identification: Friend or Foe (IFF) signals to track their movements.
- In the Ruby/Sapphire arc of Pokémon Adventures, Intrepid Reporters Gabby and Ty are horrified when they realize their boss is Archie and has thus prevented any news of Team Aqua's crimes to go broadcast. What's more, they witness him and Maxie teaming up and deciding to go to the Cave of Origins together in a stolen submarine. Gabby immediately wants to announce the truth to the rest of the news station, but Ty points out that if their boss was the leader of Team Aqua, it may already be filled with undercover grunts and the two of them wouldn't know who they could trust. Thankfully, in a slight aversion, the two decide to ditch the news station entirely to inform the people they know they can trust: the Gym Leaders.
- In the Mobile Suit Gundam sidestories known as MSV, there is a Mobile Suit called the GM Camouf, which was a Zeon MS designed to look like a GM to fool the Federation. However, it proved to be a disaster when a group of Camoufs were destroyed by their own Musai transports!
- The modded "Zeta Zaku" by Iino in Mobile Suit Gundam ZZ has a Zaku II's head in the place of the Zeta's (the Zeta's head was damaged and a long-abandoned Zaku was the only thing they had on hand for repairs). Despite the Argama crew's concern the resemblance to an infamous Zeon Mook Mobile would cause a friendly-fire incident, Iino assumes he'll be fine because their enemies aren't currently using any. Comically, it's Judau who's confused and starts firing at it in his shock, even though he'd never fought a Zaku before!
- In Mobile Suit Gundam Wing, the five Gundam pilots start out wary of each other and sometimes end up fighting among themselves after destroying their mutual enemy. None of them were told by their handlers that there would be others like them, so the Heel–Face Turn they all had concerning the objective of their mission prior to launch made them into each other's potential enemies, since they had no way of knowing whether the other Gundam pilots were still adhering to the original, rather genocidal mission plan. Unlike what the fandom would have you believe, they don't come together as a five-man team until near the end of the series, but they do often work in pairs of varying combinations once the misunderstandings are cleared up.
- In the Back Story of Mobile Suit Gundam 00, Sumeragi and Mannequin mistook each other's forces for the enemy and effectively obliterated their allies before realizing it. Both were deemed not at fault due to having been supplied with bad intelligence, but it still weighs heavily on both. Sumeragi's love interest died in that battle, too.
- In episode 12 of Martian Successor Nadesico, the Nadesico fires on both Jovian and UEAF ships during one battle. At first it confuses everyone as to why the ship did that, but it turns out that the Nadesico has a learning computer, and still retains information that the UEAF is considered hostile (due to their actions in preventing the ship from going to Mars in earlier episodes). The UEAF attempts to reprogram it, but Ruri disagrees, since formatting the computer would cause it to lose valuable combat data it acquired when they went to Mars. So she decides to reprogram it herself with the help of Akito and Seiya to allow the Nadesico to retain its information, while simultaneously erasing the UEAF forces as hostile.
- In Tintin: The Red Sea Sharks Tintin and his friends make an escape riding camels. Mull Pasha (Tintin's old foe Dr. Müller), head of Bab El-Ehr's forces, phones his air force commander to send a squadron of Mosquitos after them, adding "armoured cars are already on their way". Due to a misunderstanding, the Mosquitos fire on and destroy the armoured cars pursuing Tintin and co.!
- In The Avengers, after Hercules had been rendered comatose, Zeus brought the Avengers to Olympus and attacked them. A figure came to their aid, and Zeus fought him for some time, before he realized it was Hercules, risen from his sick bed to help his friends. Zeus is deeply grieved by his folly.
- The orkish view on friendly fire is seen in Deff Skwadron, when the squad commander of deff skwadron chastises one of his gunners when he baulks at firing into a pitched dogfight where telling who is on which side is impossible. Essentially it boils down to "shoot at everything, and if you hit anything it must obviously belong to the enemy."
- In Fury: My War Gone By, Nick Fury and his partner Heatherly is stuck on a French base in Vietnam, then called French Indochina. They come under heavy assault by the locals, and the battle gets close and messy. Eventually, the locals are driven back. After the battle, Heatherly says he's pretty sure he shot a friendly.
Nick Fury: I'm pretty sure I did too. Sometimes it just gets like that.
- When under the effects of the Trigger Scent, X-23 enters a berserker state where she tears apart everything in her path, and when she's in her rage she blacks out entirely, and is completely unable to distinguish friends from foe. It's been exploited by villains on multiple occasions to force her to hurt people she cares about.
- The Transformers (Marvel): One notable example comes in the Christmas story "Cold Comfort and Joy". The Autobot Powermasters track down a group of robots who spoiled a town's Christmas festivities, assuming they're Decepticons, and it isn't until Joyride notices the Autobot symbol on the chest he's pounding that they realise their mistake. (The Autobots were just trying to join in the fun but the townspeople all went "Aargh! Giant robots!" anyway.)
- In Robyn Hood: I Love NY'' #3, Robyn and Agent Red are both sneaking into the same club. Not knowing who is coming, Red detonates a flashbang. Blinded and deafened, Robyn then attacks the person who threw the flashbang, not knowing it is Red.
- Played with in regards to The Incredible Hulk as there are many instances where he's so enraged he's basically lashing out at whoever is in his vicinity, even if they were on somewhat genial terms before he started going nuts.
- Averted in Batman: Year One: when Branden's SWAT team are searching a ruined building for Batman, they prepare to fire through a suspiciously closed door. One of the officers gets on the radio and alerts the other officers that this is precuationary fire only.
- Discussed in the Marvel NOW! launch of Thunderbolts. When Agent Venom is recruited, he notices the other members are already in red and black and has the symbiote adjust, turning the white parts red. Deadpool calls him a suck-up, leading Venom to throttle him and tell him that using the same color lessens the chances of friendly fire.
- In Judge Dredd, one of the tactics used by the Special Judicial Squad (the Judges' version of the Internal Affairs Bureau) is the "Random Physical Abuse Test", where a team of SJS Judges randomly abduct a Street Judge, drag them into a holding cell and torture them as an impromptu test of the Street Judge's ability to withstand interrogation. In issue #826, the problems with this test are highlit when the targeted Street Judge, having survived the events of Necropolis, presumes the attacking SJS Judges are assassins, grabs her gun, and shoots them dead on the spot. The plot of the issue revolves around the higher ups arguing about what's a suitable punishment for her, or even if she deserves a punishment.
- Inverted in the Fire Emblem: Three Houses fic Goddess Against the Church. When Byleth refuses to kill Edelgard and Rhea goes murderously berserk in the Holy Tomb, all hell breaks loose, Byleth's allies start trying to kill each other, and a panicking Mercedes starts healing both sides indiscriminately.
- The Dressing as the Enemy tactic used by the German soldiers at Bastogne in Battleground (1949) forces the real American soldiers to do this a lot. One encounter between the American protagonists and some other Americans in a jeep leads to a comic exchange in which they're challenging each other to prove themselves by asking how the Brooklyn Dodgers did last season or who Ginger Rogers is dating.
- In the battle royale at the end of Blazing Saddles, The Waco Kid punches Black Bart before realizing who he is. He pats his cheek by way of apology and then throws himself back into the fray.
- Played straight in the German film Berge in Flammen ("Mountains Aflame", 1931), set in World War I in the Alps. Austrian soldier Florian Dimai, played by Luis Trenker (who also co-directed the movie and wrote the semi-autobiographical novel on which the screenplay was based) returns from a dangerous reconnaissance behind enemy lines with the news that the Italians are about to blow up a giant mine beneath the Austrian positions and is shot in error by one his own comrades who mistakes him for an approaching Italian soldier. He still delivers his message and the men leave the position in the nick of time before it is blown to smithereens, but in the epilogue set in 1931 Dimai has only one arm.
- Played with in The Longest Day. Allied paratroopers are given clickers used to identify each other without speaking (just as in Real Life in World War II) - two clicks will be answered by two clicks from a friendly soldier. A lone paratrooper hears an approaching person, clicks twice, and hears two clicks in return. He stands up in relief, and is shot and killed by the approaching person - a German soldier. The Reveal happens when immediately afterwards, the German soldier works the bolt action on his rifle - producing two metallic clicks.
- Played for Laughs in Black Hawk Down: Three Rangers have been separated from the convoy, and are making their way through the city (two machine gunners as a pair, and one rifleman on his own). The one rifleman gets shot at, and is quick to share his opinion of the two gunners.
[after being shot at]:
Twombly: Say who?
Yurek: It's Yurek! You almost killed me, you fucking assholes!
Twombly: ...well, uh, come to us!
Yurek: Fuck you! Come to me!
- Played straight in Hamburger Hill: a green lieutenant is shown to be having trouble locating his position on a map while calling in an airstrike. Huey gunships then fly in and gun down the advancing American soldiers.
- In the After Action Patch Up scene at the end of El Dorado, it's revealed that the injury Cole Thornton received in the leg during the climactic gun battle was from Mississippi's Sawed-Off Shotgun.
- In Joseph Vilsmaier's Stalingrad, during the assault on a factory, von Witzland's unit engages in chaotic close combat and one of his soldiers accidentally kills a comrade. Another one remarks that the hapless killer shouldn't feel too sorry, because this happens to everyone.
- Used in several scenes in Kelly's Heroes:
- Kelly's platoon is bombarded by their own side's artillery repeatedly, thanks to the incompetent Mulligan getting the coordinates wrong.
Big Joe: [yelling at Mulligan over the radio] No the Krauts are not here! We're here!
- German officer Colonel Dankhopf is shot by one of his own Tiger tanks after he drunkenly wanders over towards it during a battle and gets mistaken for an American.
- When the platoon is behind enemy lines, an American fighter plane attacks them repeatedly and destroys their Jeeps and halftracks, mistaking them for Germans.
Crapgame: Hey! Hey! That idiot's one of ours!
Big Joe: Oh. Our hero.
- Kelly's platoon is bombarded by their own side's artillery repeatedly, thanks to the incompetent Mulligan getting the coordinates wrong.
- This happens to Major Schroeder in Force 10 from Navarone after he gets taken prisoner by the Allied commando team. His men ambush them in the hall and shoot at his captors, but only succeed in accidentally killing him.
- At the end of Under Ten Flags (1960), a British officer who's a POW on the German raider notes the irony that he's dying from a British shell splinter (from the cruiser that's firing on them), and points out to Captain Rogge (who's tried to fight the war in a civilized manner) that such decency isn't possible in modern warfare.
- Exploited by 007 in Thunderball. Finding himself between two groups of the Big Bad's men, Bond takes a shot at each, then quickly ducks out of the way when they open fire in each other's direction.
Largo: Stop it you fools! He's got you shooting at each other.
- The Assignment (1997). The protagonist is a Doppelgänger for infamous terrorist Carlos the Jackal, so he's recruited for a CIA/Mossad intelligence operation. His impersonation works so well he's mistaken for the real Carlos by French anti-terrorist agents and has to shoot his way out.
Shaw: The French made it perfect for us. The KGB now think you're Carlos. They took the bait!Annibal: You fucking maniac. Jack, I-killed-four-men! (as Jack looks away) HEY, I DON'T LIKE KILLING OUR FUCKING ALLIES, ALL RIGHT?Amos: Policemen wind up killing other policemen. It happens. I'd rather have you here feeling guilty about them then to know that there's some meeting in Paris with them all sitting around feeling guilty about you.
- Invisible Avenger: After the Shadow turns invisible on the yacht, Victor panic fires when he sees movement and hits his all the Colonel instead. The Colonel assumes this is a deliberate act of betrayal and delivers a Last Breath Bullet to Victor.
- In Die Hard this, along with a metric ton of other bad things, happens to poor McClane when he's trying to save the hostages who have been herded onto a roof rigged to explode. He begins firing into the air to scare them back down the stairs just as a police attack copter flies up, and they open fire on him believing him to be a terrorist.
McClane: I'M ON YOUR SIDE, ASSHOLES!!!
- In The Beasts Are on the Streets, Jim is hunting lions in the forest at night when he sees yellow fur and fires. It's the blond hair of his teenage son Hal, who ends up needing surgery.
- In Moving Violation, Rankin starts shooting at a police car that he thinks was stolen by Eddie and Cam. He doesn't realize until he's run it off the road that it's actually being driven by Deputy Frank.
- This sets up the plot of Insomnia. A detective hunting a murderer accidentally shoots his own partner and makes the mistake of covering it up. The murderer witnessed the incident and uses it to manipulate him to his own advantage.
- Another comic example is the sketch in Rutland Weekend Television where a guard asks a man in a carrot suit "Are you friendly or foeful?" The carrot man replies that a more correct challenge would be "Art thou friend or foeman-carrot?" After a lengthy discussion about the correct adverb of "foe", the carrot admits he's a friend.
"So we didn't need the bloody lecture on "foe" after all, then!"
"Only a friend will help you with your grammar."
- In the finale of Battlestar Galactica, in order to distinguish between friendly and enemy Centurions, the colonials use the simple method of slapping a red sash of paint on their friendlies, which had the advantage of making them look even more badass.
- The X-Files: Agent Scully, in an effort to salvage her career, is paired with a young up-and-coming FBI agent. Who shoots a murder suspect who turns out to be holding a camera. Not only that, the bullet goes through his body and hits Scully. One assumes his career took a nosedive after that.
- It's also a common trope for the show in general. The tagline is "Trust No 1" for a reason. It's very hard to keep track of who is friend and who is foe, especially since that changes from week to week.
- Played for comedy and subverted in Do Not Adjust Your Set. The exchange went:
Guard: Halt! Who goes there, friend or foe?
Guard: Uh...oh! [shoots]
Officer: [stumbles on-screen, speaking carefully] Well done, Foster... just checking. [collapses]
- Happened on Meerkat Manor, when the two halves of the drought-divided Whiskers clan were about to attack the "strangers" they'd spotted in the distance, but fortunately recognized each others' clan scent before any harm was done. Justified by meerkats' poor distance vision and intense territoriality.
- An episode of M*A*S*H ('C*A*V*E') dealt with the 4077th's issues with a well-meaning artillery barrage. It's not the only time it happens.
Klinger: Halt! Who goes there? Friend or foe?
- In another episode, Klinger is on guard duty when Margaret speeds in with an injured Col. Potter in tow:
Margaret: Out of my way or I'll run you over!!!
Klinger: Pass, friend.
- Star Trek: Deep Space Nine:
- In "A Time To Stand", the crew are taking a captured Jem'Hadar ship on a covert mission when they are attacked by the Federation ship USS Centaur. Fortunately there is little damage on either side.
- And invoked in another episode, "Paradise Lost", where the USS Defiant is engaged in an inconclusive battle (neither side was ultimately willing to use enough firepower to destroy the other ship) by the USS Lakota, due to the latter ship's crew being given false information that the Defiant had been taken by Changelings.
- In "The Siege of AR-558", Sisko and his officers beam down to the titular planetoid to bring supplies to combat-weary Federation soldiers and are quickly fired on by said soldiers. Fortunately, their CO orders them to cease fire before anyone gets hurt.
- Star Trek: Voyager. Played for Laughs in "Message in a Bottle" when two squabbling EMH's are trying to work out how to pilot an experimental Starfleet spacecraft in the middle of a fight between Starfleet and Romulan vessels. At one point they launch a photon torpedo without properly aiming it first, causing it to hit a Starfleet ship rather than a Romulan one.
EMH Mk 1: You hit the wrong ship!
EMH Mk 2: It wasn't my fault!
EMH Mk 1: Then whose fault was it, the torpedo's? You're supposed to tell it what to do!
- Star Trek: Enterprise: During a space battle between Vulcans and Andorians, with the Enterprise joining the fight on the Vulcans' side, one of the shots hitting the Terran ship is clearly coming from the Vulcans (Andorian beams are blue; Vulcan beams are green; Terran beam are red — the color of their respective blood). This is not commented upon, though.
- In the Supernatural episode "Devil May Care", Kevin shoots an arrow at Dean when he enters the bunker before he realizes who Dean is.
- In the Stargate Atlantis episode "Phantoms", Sheppard's team goes to an unfamiliar planet on a rescue mission and finds themselves under the influence of a Wraith mind manipulation device that makes them hallucinate. As a result, Sheppard thinks McKay and Ronon are enemies and shoots them both (nonfatally). This is played for laughs near the end of the episode.
Rodney: You shot me!
Sheppard: Yes, Rodney, I shot you, and I said I was sorry.
Ronon: You shot me, too.
Sheppard: [exasperated] I'm sorry for shooting everyone!
- On The 100, Clarke convinces Anya that she should work with the Sky People instead of fighting against them; Anya is killed almost immediately afterwards, shot by Sky People who didn't know she wasn't still their enemy.
- Part of the backstory of Flashpoint character Sam Braddock. He was a long-distance marksman in Afghanistan, taking out targets from over a kilometer away, which meant that he couldn't make out any detail about his targets and was relying on information from reconnaissance teams to give him the all-clear (meaning the target zone was clear of everyone but enemy personnel) before he could start shooting. For reasons that are never explained, on Sam's final Army mission, Sam's best friend somehow ended up in the target zone after Sam had been cleared to fire and took one of Sam's bullets. Despite the fact that he couldn't have known, the episodes where this is mentioned make it clear he's carrying an incredible amount of guilt over what happened.
- In one episode of NUMB3RS, Colby tells David that he was involved in an incident of this type when he was in Afghanistan.
Colby: The Northern Alliance was already in Kandahar. The Taliban was running this rear guard action out of the Shahi-Kot Mountains. There were just caves and bunkers everywhere. Seemed like every night these guys would come out and just pound us with RPGs. So, finally, one night, we decided to cut them off and set up an ambush in between the base camp and the pass where they would go up into the mountains. Only no one realized the SAS was already up there working that area. By the time they put together our ambush with their call for help, there were already two British soldiers dead.
- Fargo. Gus gets separated from his partner Molly in a snowstorm. Nervous over the gunfire he can hear, he fires blindly and hits her instead (fortunately the bullet hits her Useless Spleen). She's such a Nice Girl she doesn't hold it against him, and after a Time Skip they're shown to be Happily Married, though Gus has left the police as a consequence.
- A popular Soviet Russian song "The artillery fires against their own" with the text by Alexandr Mezhirov is about a soldier whose unit is under friendly fire from the artillery. The narrator muses the scouts must have given them the wrong directions.
- In Irish legend, when the hero Cuchulainn goes into "warp-spasm," he is invincible — but cannot distinguish friend from foe.
- In The Bible, this is how Gideon defeated the Midianite army with only three hundred soldiers. His forces surrounded their camp at night and made a big racket with trumpets and shouting and torches, which (with some divine assistance) caused the Midianites to panic and start fighting each other.
- Played for Laughs in an episode of The Goon Show in which Willium shoots at Seagoon and then asks "Friend or foe". And then there was "The Phantom Head Shaver of Brighton":
Eccles: Who's dat? Halt, who goes dere?
Ned Seagoon: Have no fear, I'm Q. C. Hairy Seagoon — defending council in the Nugent Dirt case. I have on me several documents of identification — including a letter of personal trust from the Commander of the British Army; a memo of recommendation from Mr. Anthony Eden, the Foreign Secretary; a special pass signed by Mr. Clement Attlee, Leader of the Opposition; and last but not least, a permit to go where I please signed by the Prime Minister the Right Honourable Sir Winston Spencer Churchill.
Eccles: Friend or foe?
- In The Hitchhiker's Guide to the Galaxy (1978) radio series, Arthur is asked this, to which he sensibly replies, "Do I know you?... Well, without knowing you it's hard to tell. I mean I quite like some people, others, not so much." He later goes on to explain that very few of his friends "have piercing red eyes, black armour, and laser rifles."
- The Tactical Shooting supplement for GURPS warns us that this is a very real possibility in a chaotic and poorly lit gunfight.
- Warhammer 40,000:
- Khornate berserkers are out for blood (for the blood god!) and skulls (for the skull throne!), and they don't care whose. This includes all the World-Eaters traitor Legion — among whom Kharn The Betrayer is particularly noteworthy, having attacked his own legion as well as the enemy when both sought shelter against deathly cold rather than fight on. Kharn's own brand is even reflected in the rules; he never misses his swings, if the dice say he missed he just buries his axe in one of his soldiers instead. Despite this, he's a pretty fun guy.
- And there's also the Chaos Dreadnought who every turn has a chance to go batshit crazy and turn all of his available weaponry on the nearest target regardless of affiliation, because unlike Loyalist Dreadnoughts, they don't get to sleep for the centuries between battles, they get their limbs and weapons removed and get chained to the wall, aware of every passing second.
- Orks as well, though in their case it's less "kill for the dark gods" and more "hah, lookit those gits gettin' shot". Orks are attracted to loud guns and enormous explosions, so if they come from their own side not matters little, being an acceptable risk in the endless cycle of fighting, looting, and shooting that is an ork's happy life.
- Some background material notes that there have been Imperial friendly fire incidents due to Mechanicus icons usually being red, and enemy icons also being red.
- In in-game mechanics however, the trope is averted by the same vein as Warhammer, with no units being allowed to use ranged attacks upon units in engaged in a melee and risk hitting their allies. However, Blast weapons missing could potentially end up accidentally hitting allied units from scatter moving the targeting circle onto them.
- Warhammer: for balance reasons, units in melee can't be targeted by ranged attacks, averting this trope. Played straight with the Skaven, who as a race of backstabbing ratmen, can fire into melee (with a random chance of hitting friendlies).
- Many gamers will have a personal story of being toasted by an overeager ally with more fireball radius than he intended. Later versions of the games (especially those with magic-produced kabooms) even start adding abilities that allow true friendly fire; how about a raging inferno, 40 feet across, with built-in 5-foot safe squares in a random pattern?
- The first casualty in Red vs. Blue? Church, of the Blue army. The shooter? Caboose, also of the Blue army. Church is not pleased.
- Escalates to a two-way Running Gag: Church getting injured by his allies, and Caboose being a prolific team-killer (by virtue of clueless incompetence, not malice).
Washington: (On reporting a deceased Freelancer to Command) I told them Caboose did it. Apparently they already have a shortcut on their keyboard for reporting his team kills.
Caboose: (blithely) Control-F-U.
- Escalates to a two-way Running Gag: Church getting injured by his allies, and Caboose being a prolific team-killer (by virtue of clueless incompetence, not malice).
- In American Barbarian, Two Tank Omen sends his prisoners toward his enemies, leading them to think the prisoners are his allies — and they attack them.
- Digger: In chapter 2, Digger and Shadowchild come across a village that's been hit by bandits. As they make their way through, they hear fighting in the distance. Shadowchild wonders if they should go help, but Digger points out the difficulties in determining the alliances of strangers in the heat of battle, instead opting for them to carefully pick their way along and look for any survivors they could help.
Digger: Go help who? How do we even know what side we're on? And if this is some kind of raid, I'm pretty sure both sides are going to be stabbing first and asking questions later. If at all.
- The Embodiment of Sins: Ish's goblins don't believe him when he tries to explain how he was turned into a humanoid female, and he's forced to cut his way to safety through his own warband.
- In Freefall, satellites use IFF to differentiate ships from space hazards.
- Girl Genius:
- Agatha gets questioned before she gets helped.Context (some spoilers)
- The Jägers have a very direct way of solving this problem.
- In Kevin & Kell, the hunting team takes part in a "blind stalk", in which they hunt in total darkness, guided only by their sense of smell. Vin, a jealous member of the team, tries to get revenge on Rudy by putting prey pheromones on him, and Rudy manages to avoid his teammates long enough to lure in a deer (who mistakes him for a doe) and take his antlers. It initially appears that Vin was mistakenly eaten by Rudy's teammates, but it is later revealed that he was abducted after stumbling onto the Great Bird Conspiracy.
- Comes up regularly as a topic of discussion in Schlock Mercenary, usually as an explanation for why Schlock can't have more or bigger guns. Exploited in an early storyline: when hired out by two local gangs at once, they get the gangs to wear IFF tags to avoid being inconveniently shot by their mercs (who "don't know your 'homeyz' colours from crapstains", direct quote)... and then use the tags to make it easy to round up all the gang members and complete a contract for local law enforcement.
Maxim 15: Only you can prevent friendly fire.
- Unknown Lands: Inara shatters Vard's arm and breaks his nose when the trio first approach the champion since she mistakes them as being part of the group of hunters that were just trying to kill her. After she's had them all swear themselves to act as guards for a year in return for her aid one of her more wide range attacks nearly takes off his arm while he's fighting with his back to her with him only being saved because the group's other mage yanked him out of the way.
- Avatar: The Last Airbender seems to have a villain-induced variant: In the episode "Zuko Alone", one of the soldiers mentions that the Fire Nation will often put captured prisoners in Fire Nation uniforms before placing them on the front lines of an assault unarmed, causing their own comrades to unknowingly slaughter them, believing that they're the enemy.
- In "The Boiling Rock", Sokka is disguised as a prison guard, and becomes victim to this trope, twice.
- The Hair Bear Bunch: In "King Klong Vs. The Masked Marvel", Botch asks the drivers of an arriving truck if they are friend or foe. They're from a rug cleaning company, so Botch lets them pass as friend.
- My Little Pony: Friendship Is Magic features the Changeling, a species of shapeshifting monster. In one episode, they disguise themselves as the heroines and engage them in a fight, where it is hard to tell who is fake and who is real.
- The episode "Snafuperman" of the WW2 soldier's educational cartoon Private Snafu had Snafu refuse to read his maps or field manual, and gets magicked into a Captain Ersatz of, as the name suggests, Superman by the Technical Fairy. He attempts an air raid on Washington DC under the misconception it was Berlin, and attacks an American tank thinking it's a Japanese one.
- The animated Punky Brewster episode "Double Your Punky" has the titular girl battling an obnoxious clone of her that Glomer accidentally created from a photograph. Glomer is unable to tell which is the real Punky so he can zap the other back into the photo. Punky's dog Brandon picks her out immediately, recognizing her scent.
- Season 5 of Samurai Jack: Many people whom Jack had met and inspired nearly attacked Ashi, as she could have been mistaken for one of Aku's servants.
- Star Wars: The Clone Wars: This gets intentionally invoked in "Carnage of Krell". General Krell first sends the 501st to intercept a group of Umbarans who have disguised themselves by wearing clone armor, then sends a message to the 212th, telling them that a disguised group of Umbarans is heading their way. Predictably, when the two groups run into each other in the jungle, both assume the other to be the disguised enemy and open fire. When Rex finds out that one of the "enemy" corpses is a clone and starts screaming at everyone to stop firing, both groups realize their mistake, but that realization comes too late for the multiple troopers who have already been killed.
Rex: Everyone, stop firing! We're shooting at our own men! They're not Umbarans! They're clones! Take off your helmets! Show them you're not the enemy! They're clones! Everyone, stop firing! Cease fire! They're not Umbarans! They're clones! Look! We're clones! We're all clones!
- Transformers: Animated episode Lost And Found: Blitzwing and Lugnut are fighting the Autobots at the bottom of a lake. When the lake gets muddied up from the fighting, Lugnut sees a dark figure and punches it...
Blitzwing: Whose side are you on?
- The Wild Thornberrys had this in one episode, where for a battle, Eliza and Darwin placed two groups of monkeys, one with long tails and one with short, in coconut-shell armor. When the monkeys went to fight, they couldn't tell friends from foes and attacked both, to prove Eliza's point that they weren't that different, and the whole "Tails vs. No tails" thing was completely ridiculous.