The word "fool". Try it out. When someone disappoints you or does something stupid, throw the word out. C'mon, give it some gusto. You fool! You...(deep breath, now) FOOL! Got the hang of it yet? No? It just sounds silly in real life? Well, get used to it, because fiction? Fiction loves this word. It's the ultimate insult. Every villain uses it, every hero with a hasty friend uses it...Hell, if we were to list every example we could find, it'd just overflow the page. It's so common. Only really prominent examples should be listed.
Interestingly, we may have the Hays Office's old Production Code to thank for this. In the olden days, most mainstream works couldn't use profanity. How to show that your villain is one bad dude when his language is carefully scrubbed with bleach? Well, according to The Bible, whoever says "You fool!" is in danger of the Lake of Fire. (Matthew 5:22) Thus, having your villain call his rival a fool allowed the audience to know that this guy was bad news without resorting to using any verboten words.
Common contexts:
"FOOL! Did you really think you could harm me!?", as said by the Bad.
"You fool! You've doomed us all!", as said by the Bad's advisors to him when he activates the superweapon.
"You really think this is about money? Don't be a fool," in cases of motive misidentification.
"Foolish mortal!" in case the one who said it is a greater being than human.
"Foolish Fool!" for when the person and their actions must be lauded.
In Dragon Ball Z, Son Goku yells this at Frieza just before finishing him off with an energy wave when he refuses to give up the fight. This was Frieza's secondBackstab Backfire, after Goku had both invoked Cruel Mercy and then saved Frieza's life after he cut himself in half.
Earlier, he also made the following remark due to Pippin's curiosity in the Mines of Moria giving their position away, "Fool of a Took."
Later, Boromir uses it when Frodo refuses to give him the Ring: "You fool! It is not yours save by a happy chance! It could have been mine! It should be mine! Give it to me!"
Mortal Kombat: Shang Tsung says this a lot whenever someone fails him. Also said it when Liu Kang punched him in the face. Ironically it made Shang Tsung look like the fool not Liu, since the whole point of Mortal Kombat revolves around hitting your opponents.
Literature
The Lord of the Rings employs the term a lot. Gandalf's fond of handing out "You Fool!!" and Pippin seems to receive them regularly.
In Moria: "Fool of a Took! Throw yourself in next time, and rid us of your stupidity!"
At the bridge of Khazad-dûm: "Fly, you fools!"
After Pippin's foolishness leads him into inadvertent mental contact with the Big Bad, Gandalf examines him for signs of Mind Control and then says, "A fool, but an honest fool, you remain."
In "Harry Potter and the Goblet of Fire", this is Professor McGonagall's reaction to Fudge refusing to believe Voldemort has returned: "You fool! Cedric Diggory! Mr Crouch! These deaths were not the random work of a lunatic!"
Susan Calvin in Isaac Asimov's "Little Lost Robot":
"Robots have learning capacity, you . . . you fool—" And Bogert knew that she had really lost her temper.
At the climax of the second Warrior Cats series, Hawkfrost informs Brambleclaw that he is a fool... and stupid.
"Fool" shows up a lot in Animorphs. It's treated as the ultimate slap in the face when Alloran tells off Seerow for giving the Yeerks technology. Visser Three likes to yell "Fool!" and its variants at his underlings a lot, also. Usually about three seconds before offing the sucker.
In the Dragonlance novel Dragons of Spring Dawning, Laurana repeatedly calls herself a fool after realizing that she has allowed her Arch-Enemy Kitiara to trick her into getting herself and her friends captured.
...which was based on Mr. T's classic Catch Phrase.
This classic Hollywood Squares clip, where the Epic Fail of the contestants led to the panel calling them fools as a Running Gag. (To elaborate, Gilbert Gottfried was the last square available and a contestant would only have to answer his question correctly to win. They couldn't, failing seven questions in a row. The first time, Gilbert shouted "You fool!" mimicking Penn Jillette's Chewing the Scenery; and soon the entire panel was joining in.)
Another one in Next Generation: The Enterprise encounters a Klingon vessel whose crew had been placed in suspended animation almost a century earlier and doesn't know about the truce with the Federation. Worf and Klingon Emissary K'Ehleyr pretend to command the Enterprise to deceive the crew into thinking the Klingon Empire was victorious.
Worf: You fool! Did it not occur to you that the war would be over by now?
Star Trek: The Original Series episode Day of the Dove. Kirk has just explained to the Klingon captain Kang that the Enterprise is under the control of a creature that feeds on hate and wants the Klingons and humans to fight for its entertainment for the rest of eternity. Kang decides to fight Kirk anyway, at which point his wife Mara exclaims "You fool!".
Later, Kang himself admits "Only a fool fights in a burning house."
In the last episode of The Middleman, when the Middleman learns what the doll's eyes were made of, he shouts " Eyes Without a Face! You fool!"
Around the start of the 8th season of Scrubs, one of JD's fantasies, didn't end well for Dr. Cox. When he snapped out of it and looked at his mentor, he commented, "You proud fool!"
Lord Dread has done this at least once in Captain Power and the Soldiers of the Future, most notably when Hawk's diversion prevented the Bio-Dread Soaron from destroying Power's ship during the run on the Icarus Control center.
Mighty Morphin' Power Rangers: Rita Repulsa and Lord Zedd would frequently call their minions fools when browbeating them.
In an episode of the Drew Carey Show, Kate caught Drew cheating on her with an old girlfriend. Later in the episode, Drew drops in on Oswald and Lewis and tells them that Kate's pissed and looking for him.
Lewis: You fool! You've killed us all by coming here!!!
Music
In The Protomen, Protoman is fond of calling humans fools. Cause they are.
In Act II, Dr. Wily calls Light a fool for thinking humanity will resist him.
In the musical segment of Cheech And Chong's "Earache My Eye", the singer (Glam Rock parody AliceBowie) shouts maniacally at the end of his song, "Watch me burn, ha ha ... YOU FOOLS!"
Stand Up Comedy
In a stand up act done by Bill Cosby, he recounts how he and his friend "Old Weird Harold" went to see a horror movie marathon and had to walk home after dark. They were frightened by the sudden appearance of a wino and beat him up before running away. Bill imagines the wino making an accident report:
Cosby: Now I'm sure, while filling out the accident report on this man, that the doctor said, "What happened?"
"I don't know. It's just, four feet ran right up my chest, danced on my head for a half-hour and then ran straight down my back, doctor."
"Well did they say anything?"
"Yes, they said, 'WAAAAAAAAAAHHHHHHHHHHH!'"
"Did you see them at all?"
"Yes, there was a little kid riding on top of a tall skinny one and he was beating him with a stick saying, 'Faster, faster, you fool, you fool!'"
Franziska von Karma from Phoenix Wright: Ace Attorney took this to new levels by not only turning it into a Catch Phrase, but making it redundant to the point where every few sentences would be something along the lines of "Foolish fool with the foolishly foolish ambitions of a foolishly foolish fool..."
Franziska: Foolishly foolish fool with foolishly foolish fool ideas of foolish tomfoolery... Franziska: ... You're so foolish, you've even made me sound like a foolhardy fool...
Edgeworth gets at least one instance of this as early as 1-2, in response to the bellboy revealing, on the stand, that Edgeworth instructed him not to reveal that there were two people at the hotel.
Dragon Age II: Orsino declares "You fool, you've doomed us all!" after Anders destroys the Chantry.
Commander Kielbasa to Roger Wilco in Space Quest VI:
Kielbasa: WILCO, YOU FOOL!
Used in the original Myst and Myst IV by Magnificent Bastard Sirrus, the former as a number one in a Bad Ending (You've done the right thing. You stupidfool!HAHAHAHAHA...), the latter as something of a number two: (No, you fool! My performance was perfect!).
Many of the tablets in La-Mulana call the player a fool. One repeats "Thou art a fool" four times.
Ecstatica II had a female voice tell you "Cease this madness, you fool!" if you tried to hit switches before they were able to work.
Xenosaga: Episode III: At the end, KOS-MOS breaks Shion's Mineral MacGuffin, the Cosmic Key of Reset. Wilhelm says, "You fool." It's notable not just for coming at the climax, but for how softly it is said. The delivery fits the deliverer perfectly.
If you screw up entering the dimensional portal near the end of Half-Life: "Freeman, you fool!"
Lemonhead: You fool! You've given cheese to a lactose-intolerant volcano god! Do you know what that means? You've brought about the coming of the Divine Dysentery! Run for your lives!
Xemnas is even more fond of it, considering during one of his fights, he shouts "Cursed FOOOLS" at the party.
Saix utters a simple "Fool" when Maleficent summoned Heartless to attack him, and then summoning Nobodies to dispatch them afterwards.
Emil pulls this on Marta in Tales of Symphonia: Dawn of the New World during her depression induced stupor regarding Ratatosk's Core and its possible effects on her. The "You fool" bit tips her off that it's really Ratatosk-Emil talking, not regular Emil.
In Eternal Darkness, Pious calls Ellia a fool twice, first for being so close to Mantorok and then for not following his advice to run away.
Garland from Final Fantasy I calls out the Light Warriors as impertinet fools right before the knockdown.
LIGHT WARRIORS?? You impertinent fools. I, Garland, will knock you all down!
In Diablo 2, Tyrael uses this when Marius takes Baal's soulstone. 'You... FOOL! You have just ensured the doom of this world!'
Kerrigan in Starcraft II will repeat this phrase or a slight variant of it many, many times during the campaign.
One of the bosses in the old arcade game Kid Niki: Radical Ninja, the Mad Monk, uses this phrase as his primary weapon. He can say it softly and drawn out ("Fooooooooollll..."), extending across the top of the screen to drop Os on you; he can shout it out as a large kanji with which to crush you; or he can scream, "GET HIM, YOU FOOLS!" to summon some mooks to take you out, or at least keep you distracted enough to fall for one of the first two.
Lord Victor Nefarius, aka the Black Dragon Nefarian from World of Warcraft gives us this Genre Savvy line when he berates his incompetent minions:
Subverted, though, by the time you face Nefarian himself, he has forgotten his own advice for your convenience.
It makes sense, though - when you're watching a fight, figuring out who the biggest problem is easy. When you're the one getting smacked upside the head by a guy wearing plate armor, but the guy in the dress is doing nothing visibly harmful to you, which would you reasonably go after? He makes up for it somewhat, though; instead of trying to kill the medics first, he screws with them in various ways (Priest heals can suddenly start to cause damage over time to the targets, druids can be forced into cat form, etc.).
Used by the Spy in Team Fortress 2 as one of his responses, upon dominating an enemy Spy. Given the air of sophistication and competence the Spy tries to maintain, he treats this this as a grievous insult.
"You are an amateur and a fool!"
Shows up in Half-Life 2 as Doctor Breen's final words.
In The Elder Scrolls V Skyrim, a Dunmer trapped in a Giant Spider's web offers you a MacGuffin for cutting him loose. When he's freed, he says, "You fool. Why should I share the treasure with anyone?" before running further into the dungeon (most likely to get to the door the MacGuffin is supposed to unlock). If the player doesn't get him, the draugr or the booby traps will.
Web Original
Red vs. Blue: O'Malley, in his quest to over-do every single supervillain trait he could, delivered this line:
O'Malley: "You foolish fools will never defeat me! You are far too busy being foolish!"
Because the idiocy of his AI teammates, (At least in their inability to throw a flash grenade more than a foot into the room) this has become Noah Antwiler's phrase of choice during his Let's Play of ''SWAT 4''. There's even a shirt.
Lampshaded once when Spoony does it to himself and instead says "Erm, me fool!".
In a review for Sonic Free Riders by Angry Joe, Joe complains about the terrible menu controls, and preempts any viewers who think the Kinect's voice command system is any better.
Joe: Oh really?! FOOL!
Western Animation
Aku from Samurai Jack has made "FOOLISH samurai!" a meme.
Gandalf called himself a fool for not figuring out the word to open the Doors of Durin... in the rather flawed Bakshi animated movie, that is.
"Fly, you fools!"
Or the Sev cartoon parody, "I can't fly, you fools!"
In the Irregular Webcomic! parody, a character remarks that he always knew the character who said that would go out with an insult.
Cobra Commander - Foolish Joes! (insert minion's name here), you fool!
For that matter, most of Megatron and Cobra Commander's high ranking minions would call whoever was thwarting their plans a fool too.
Skeletor to Beast Man: "You furry fool!" Also, memorably parodied by Bam Margera's band, Gnarkill.
I think Venger, the big bad from the Dungeons & Dragons cartoon, would often call the heroes "Foolish Mortals".
Well, you are half right—never "mortals" that I can recall, but he called everyone "fool" or "foolish". I think he even says "foolery" once.
For that matter, pick any stock villain from the Alex Toth Hanna-Barbera action shorts from the 60s - 70s. (Space Ghost, Galaxy Trio, Birdman, The Herculoids... etc.)
Also shows up in live-action shows for kids as well. After Hawk buys Captain Power and the Soldiers of the Future time to get to Icarus Control by going after Soaron, Lord Dread, overseeing the whole thing, utters "Soaron, you fool!"
In the Beast Wars episode "Gorilla Warfare", Optimus Primal yanks a viral mine off of his chest while inside the Predacon base, prompting Megatron to yell at him "You fool! You'll destroy us all!".
Most Disney villains have called either their enemy or their minions fool at least once, likely for similar reasons to the founding uses: Disney, having earned their reputation by providing family-friendly animation in the first place, court G and at most PG ratings instead of avoiding them. So instead of profane insults you get a lot of "you fool!" and "you idiot!"
101 Dalmatians (1996):
Cruella de Vil: You're a fool, Anita! I have no use for fools.
Phineas and Ferb: At the end of "Invasion of the Ferb Snatchers", Candace once again fails to bust Phineas and Ferb, and she laments her apparent hubris in believing she could succeed in doing so.
One of Futurama's TALES! OF! INTEREST! has former Vice President and protector of the space-time continuum Al Gore shouting "You fool! You foolish fool!" at Fry, after he's just caused a time paradox that will destroy the universe.
The Real Ghostbusters episode "Halloween II 1/2" saw the guys faced with a newly freed Samhain.
Samhain: You didn't actually think you could keep Samhain, the Spirit of Halloween, locked up forever, did you, Ghostbusters? Peter: Well, yeah, actually we did. Samhain: Then you are fools! And fools deserve a swift demise!
Other
Similarly, the (for now) defunct Star Trek: The Experience attraction in Las Vegas had one of these on each of its two shows. The Klingon Encounter featured Korath angrily spitting at Riker, "Fools! You will regret defying me!" The Borg Invasion show featured the Borg Queen's admonishment when her threat of employing a self-destruct sequence is questioned, "You're a fool, Janeway! There will always be more drones."
This was the standard insult for the first few years of BIONICLE, but has lately been replaced by "idiot" and "imbecile".
"Climb you fool! Climb!" was shouted in futility at the B-25 bomber that mistakingly crashed into the Empire State Building in 1945.