A scene in which a martial artist warns an antagonist that he knows martial arts before kicking the guy's ass. Bonus points for the martial artist assuming an outlandish Ass-Kicking Pose beforehand. The antagonist will always laugh off the warnings and be defeated in humiliating fashion. If the martial artist's skills turn out not to be effective, it's probably an example of I Know Kung-Faux. These scenes were popular when martial arts films started getting attention in the west. The martial artist will almost always study an Asian style, but the trope can still hold true with any named system of self-defence.
It's pretty much a Dead Horse Trope now that Asian martial arts films and choreography have reached a saturation point in western culture. Ironically, the trope might have come full circle due to the rising popularity of Mixed Martial Arts over most classic Asian martial arts styles.
You might be looking for Suddenly Always Knew That, which used to be called "I Know Kung Fu", or the Useful Notes article about Karate. There's also I Know Mortal Kombat, where a person learns Martial Arts (or some other skill) by watching movies or playing video games.
- Subverted in Gate Keepers anime: Kageyama Reiji did this complete with throwing his jacket to the air for a good montage, even without the lines. When the jacket drops back on his hand, the thugs seemed to be hurt, until he himself collapsed. Though, he's actually the Big Bad, but a very cunning one trying to achieve a Villain with Good Publicity status.
- Saikawa claimed that she's won karate competitions when she challenged Kanna in Miss Kobayashi's Dragon Maid. She never got the chance to show it off since the sight of Kanna's fake crying destroyed her Tsundere attitude. She is shown practicing in Kanna's spin-off though.
- Beck: It's mentioned that Chiba is a martial artist, though for most of the series it's an Informed Attribute we only see when he harasses his friends with kicks and pro wrestling moves. His skills are finally put on display when he uses Karate to rescue Koyuki from a recurring villain and periodically trounces schoolyard bullies. It's even more impressive in the live action movie, when he knocks around a large gang at the skatepark. Most of the fight happens off-screen, but the bullies limp away frantically as Chiba triumphantly cheers, so it can be inferred he's just as tough as he claims to be.
- In Pre-Crisis comics was established that Krypton had martial arts.
- Villain Faora Hu-Ul knew Horu-Kanu, with which she was able to knock Superman around pretty effectively in "The Great Phantom Peril".
- Lois Lane studied the art of Klurkor in the bottle city of Kandor, and got to use it from time to time.
- Supergirl knows Klurkor in every main continuity. She has also been trained by Wonder Woman, Batman and Batgirl. In "Who Is Superwoman?" she warns Reactron she is a Klurkor first level before proceeding to kick his butt.
- Karate Kid from the Legion of Super-Heroes comics is the galaxy's master of all known forms of physical combat.
- Batman villain Scarecrow in Knightfall. No, really. It is, of course, crane style. Crane's combat style, at least per other comics from the 90's, was actually a self-taught and designed style, 'violent dancing', based around weaponizing his Crane's namesake crazy dancing from The Legend of Sleepy Hollow, part of a popular trend of retconning a lot of Batman villains during those years to have studied hand to hand combat at some point, to explain how they could actually fistfight Batman and last longer than three seconds.
- In Super Mario Adventures:
- The Minister of Massage learned his art at "the ancient Mount Fuji karate school."
- During her jailbreak, the Princess belts out a "HIEEE-YAH!", performing a surprise spin kick (in heels!) on the awestruck Koopa Kids.
- José Carioca from the Disney Ducks Comic Universe once tried to scare a bunch of criminals by claiming to be a good Capoeira fighter, only to learn one of the criminals was a master of that art. He then claimed to know Karate and was told another criminal of the bunch was a black belt.
- Inverted in Tintin album "The Black Island". Tintin is thrown to the floor by one of the bad guys, who tells him "That was jiu-jitsu!". Tintin KO's him with a kick in the chin from the floor, responding "And that's savate!" note
- Kim Possible fan fiction Zen and the Art of Ass-Whupping inverted this, playing out an alternative to one episode where the large football player was warned that the ninja knew martial arts. The martial artist naturally won. In the fan fiction though, it was turned around with the football player being a boxer, and succeeding.
- In Glorious Shotgun Princess:
- It's exclaimed by Shepard in surprise.
Pria: That's pedestrian street brawling made by peasants. You know Solar Hero Style.
- The geth have successfully emulated Shepard's martial arts using a combination of Essence and mass effect fields, creating Synthetic Hero Style.
- It's exclaimed by Shepard in surprise.
- Superman of 2499: The Great Confrontation has Katherine de Ka'an go to a martial arts instructor in order to shape up and become a better hero.
- In Mars vs. Jupiter as Told by Mina, while Lita represents pure power and strength, Raye, on the other hand, has martial arts that she learned from her grandfather.
- In Kara Of Rokyn, the titular character is extensively trained by martial arts master Lady Shiva.
- Subverted in The Return of Sherlock Holmes: Holmes warns the bruiser, "I know judo." The bruiser knows karate — and knows it better than Holmes does judo.
- Subverted in I'm Gonna Git You Sucka when the group's martial arts expert is surrounded by cops he says something along the lines of "You dare to challenge me? A master of karate, kung fu, jujitsu and all this other shit you've never heard of? Ha ha ha!" The cops respond by opening fire on him. And again later, when one of the heroes and bad guys square off against one another minus their guns, one of them hesitates and says, "I don't know any kung fu!" "Neither do I," says the other. "Want to fake it?" They then do just that.
- Parodied and subverted in Romeo Must Die when big black gangster Maurice corners small Chinese man Han. Maurice does the crane stance because "Now, you know you ain't the only one that knows some shit," and Han (or as we call him, Jet Li, the last person in the world who'd be impressed by the crane stance) immediately kicks out Maurice's supporting knee.
- That guy with the glasses in The Devil's Brigade, which he apparently wears only so he can have The Glasses Come Off.
- There Goes the Neighborhood: When Willis approaches him with the pick ax, Albert lampshades this, but not before pulling out a move in very hilarious fashion.
- In The Film of the Series of Wild Wild West, a Mook attempts to intimidate Will Smith with a series of moves he "learnt from a Chinaman". Smith then whacks him with a shovel; "I just made that up".
- This memorable exchange in Foxy Brown:
Bobbie: Listen skinny, before you start talking tough, I'd better warn you I've got a black belt in karate. So why don't you get out of here quietly, while you still got some teeth left in that ugly face?[Foxy knocks her down with a barstool]Foxy Brown: And I've got my black belt in barstools!
- In the film adaptation of Rising Sun, a bouncer warns Sean Connery that he's a black belt. Connery takes him out with a throat strike.
- Roger Moore (As Himself) attempts to threaten a thug like this in The Cannonball Run, saying: "I must warn you, I am Roger Moore" before trying an obviously fake martial arts move much like the ones he was using in his James Bond movies. It fails to work.
- In Dutch, an adolescent warns Dutch that he's a "high brown belt," then proceeds to kick his ass. Later, Dutch tries to pit his self-described "all-American streetfighting" against the kid's martial arts and loses again. He does, however, teach the kid how to throw a wicked haymaker.
- Parodied in One Crazy Summer.
Cassandra: First, you have to get through me.Kent: What do you know? Karate?Cassandra: I know Dow.Kent: Dow? What's Dow?Cassandra: Dow is the chemical company that makes mace.[She pulls out a can of mace and sprays them.]
- In the original version of Game of Death, the Hapkido master (Ji Han Jae) is the only one of the fighters to warn the heroes that fighting with him will result in death. This is very bizarre, as he should know already that they're accomplished martial artists and he's alone and they are a crowd of three.
- Ji Han Jae: As you gentlemen know, red means danger. Therefore I advice to you people, not to step into this warning arena. If you want to go on living, stop here, go back downstairs. Life is precious.
- In Torrente: El brazo tonto de la ley, Malaguita claims to be a film-level martial artist and does some random Capoeira stunts to prove it, in reference to Only the Strong.
- In the 1996 remake of The Nutty Professor, Reggie Warrington, the Insult Comic, attempts this on Buddy Love who heckled him one too many times, but Buddy anticipates his pathetic attempts to whip out his "streets skills" and Curb Stomps him.
Bryan Mills: I don't know who you are, and I don't know what you want. If you are looking for a ransom, I can tell you I don't have money, but what I do have, are a very particular set of skills. Skills I have acquired over a very long career. Skills that make me a nightmare for people like you. If you let my daughter go now, that'll be the end of it: I will not look for you, I will not pursue you. But if you don't, I will look for you, I will find you, and I will kill you.
- While You Were Sleeping. Lucy's Abhorrent Admirer claims this when he thinks that another guy is bothering her.
- Armageddon Trilogy book by Robert Rankin. This exact line is said repeatedly by Elvis (yes, that Elvis). In the books Elvis constantly makes reference to his character from the movie Roustabout, in which he knew Karate (it goes with the 'sickle).
- Also, subverted by the phrase "I must warn you that I am an exponent of Dimac, the world's most lethal martial art, and can maim or disfigure you with the mere pressure of a fingertip," because this phrase always causes the opponent to back down. Inevitably.
- It's worth noting that in real life, Elvis was an 8th degree black belt in Kenpo Karate.
- Subverted at one point with Spenser. He is questioning a female gay rights activist, and the activist bristles when Spenser inevitably goes into Sarcasm Mode. Her (also female) bodyguard decides the interrogation has gone on long enough and tells Spenser to back off or she'll use her karate to "kick his nuts into his ass". He tells her to come on, then she kicks him in the balls. She is about to attempt using martial arts on him, but Spenser is able to fight through the pain and proceeds to drop her with one punch. After she regains consciousness he instructs her on how a kick to the balls are all well and good, but if the big guy you're fighting has enough of a weight-and-strength advantage over you (and Spenser towered over her), and knows how to fight himself (Spenser really, really does), all the kicks and martial arts in the world will not help you.
- There's another moment in Stardust when a guy he's interviewing gets pissed, and has his bodyguard put on a wondrous display of karate skill by beating the hell out of a heavy bag, in order to intimidate Spenser into backing down. Spenser pulls out a revolver and shoots the bag.
- Paul Wilsen (black belt in kung fu) and Ed Summers (teaches karate) in The Unexpected Witness, though Paul doesn't explicitly say he knows kung fu until after the beatdown and Ed Summers is established about halfway through the book as being a karate instructor.
- Noah in Tsun-Tsun TzimTzum is a downplayed example. He's taken a variety of martial arts classes and even won a few minor tournaments, but in the World of Badass he finds himself transported to, that's decidedly underwhelming. It does help him in the fights he gets into, but mostly to the extent that it lets him survive long enough for his Battle Harem to rescue him.
- In the first episode of season 2 of Lincoln Heights, Cassie Sutton completely demolishes a would-be racist attacker, much to the surprise of her boyfriend Charles. Her father taught the whole family defensive tactics after the hellish season 1 the family went through. Oddly enough this is the only time any of the Sutton kids displayed any martial arts abilities despite there being numerous occasions where they are needed.
- Kung Fu did this, of course.
- Knight Rider did it at least once. Given how tall David Hasselhoff is, you can imagine just how big the local color had to be to carry this off.
- In Doctor Who, the Third Doctor was a skilled practitioner of Venusian Aikido and, despite being grey headed and somewhat frail looking, had little difficulty in physical altercations, even when facing off against several opponents.
- Subverted in an episode of Alias in which Quentin Tarantino starred. When Sydney attempts to beat him down with her martial arts skills, Tarantino susses out her style and responds with, "That's the problem with you kickboxers — none of you can take a punch." And proceeds to knock her silly with her own skillset. She later acknowledges she does need to learn to take a punch ... and kicks him in the head when he's down. (Also an aversion of Wouldn't Hit a Girl.)
- Parodied and subverted in Friends, where Ross is learning (comically overpronounced) karate. He claims to have supernatural awareness called "unagi" (actually a Japanese freshwater eel) but gets ambushed at the end of the episode.
- In Living Color! had Damon Wayans' character Anton the bum use this to try to get into the army (for the free food, of course)
Anton: I know Tai-chi! Paw-paw-paw! I know Taikwondo! Paw-paw-paw! And I know Tyrone ... yeah, he taught me all of that.
- Chuck references The Matrix above, the first time Chuck flashes after uploading the improved Intersect in the second season finale. After wiping the floor with a bunch of mooks who managed to kill Bryce Larkin, he turns in shock to an (equally) shocked Sarah and Casey and proclaims "Guys, I know kung fu!"
- Midsomer Murders: A particularly silly example occurs in "Death in a Chocolate Box". Barnaby and Jones enter a room to find the elderly Lord Holm assaulting a woman. Lord Holm drops in a boxing stance:
Lord Holm: I used to box at Eton!
Sgt. Jones: Yeah? I did karate at Causton Comp! (immediately grapples and immobilizes Lord Holm)
- Empty Nest. Carol is ready to beat up her boyfriend's ex-wife when she catches her trying to seduce him, but the guy warns her, "She's a black belt" (though the martial art is never specified).
- Sir Rodney from The Wizard of Id once tried to use this trope by telling a larger attacker that he had a black belt. Turned out the guy had the black suspenders.
- An early Garfield strip showed a mailman assuming a karate pose and warning Garfield not to attack him because he knows karate. But Garfield, being a cat, is much too small and moves much too fast for the mailman to land any blows, and bites and claws him repeatedly in a Big Ball of Violence, leaving the postman with Amusing Injuries. The last line of the strip: "And I know fast and furious."
- It's formulaic in Japanese professional wrestling, which has many martial arts/combat sports influences, that the announcer lists the wrestlers's team or background in a solemn way while introducing them.
- Part of Panama's Kato Kung Lee gimmick. An even more obvious case was a CMLL luchador who went by the name "Kung Fu". Naturally the two formed a Tag Team. They became El Triangulo Oriental with Satoru Sayama, a kick boxer.
- Subverted with Frontier Martial-Arts Wrestling, which was founded by Atsushi Onita after being turned down by the "shoot" Universal Wrestling Federation. It was to be his own "shoot" promotion and started with pro wrestlers fighting people of other disciplines but by the time it's first shows had started Onita's target had already changed from UWF to "The Japanese Mainstream" (NJPW and AJPW), leading FMW to showcase more barbed wire, fire, open electrical hazards and live explosives than martial arts.
- In one of Tyler Perry's Madea plays, one character tells Madea that she knows Tae-Bo. Unimpressed, Madea responds "And I know 'whup-your-ass!'"
- Parodied in Space Quest 5: The Next Mutation, where Roger Wilco warns the Big Bad "I know Kung Fu, Karate, Tae Kwon Do, Judo, and several other Chinese words!"
- A variant in The Riddle of Master Lu, and what would be a subversion if the audience didn't already know, where Robert Ripley basically says "My girlfriend knows karate."
[Shen Guo has Ripley pinned on the ground at gunpoint and is about to finish him off.]Ripley: I think I should warn you, you're not the only one who knows martial arts.Shen Guo: You?Ripley: Heck no! If it were me, you wouldn't be in so much trouble right now.[Mei Chen kicks the gun away from Shen Guo's hand.]
- Parodied in Penny Arcade. For extra hilarity, the guy he's talking to is Asian.
Gabe: You leave me no choice. Now, I have to do karate to you.Clerk: Do you even know karate?Gabe: I know techniques that have certain elements which have been described -- by some -- as "karate-like".
- In Pokémon Mystery Dungeon: Victory Fire, Jen, an Audino, kicks a Gengar in the stomach. When Kecleon asks what she was doing, her meek reply is tae kwon do.
- Kim Possible mentions knowing sixteen different styles of Kung Fu, and in another episode, she mentions that one of the styles she knows is Mantis-style kung fu...but it turns out she hasn't exactly "mastered" it.
- An episode of Scooby-Doo, Where Are You! has Shaggy and Scooby trying to bluff a Chinese ghost with the line "I know judo, chop suey, and Chinese checkers!" This being Shaggy and Scooby we're talking about, they later escape from the ghost's henchmen by serving them chocolate chop suey (with liver a la mode).
- In The Adventures of Jimmy Neutron: Boy Genius, Cindy Vortex is said (and shown) to know a few different types of martial arts, but mostly karate.
- In an episode of The Flintstones, Fred tries this line, only for his opponent to go, "Who is that?" before beating him up.
- Jade in Jackie Chan Adventures threatened a bully with the "ancient art of butt whoop." Considering she's the niece of Jackie Chan, you can guess how this ends up.
- She gets into trouble for thoroughly beating up the bully, who later comes back asking her to teach him. Instead, she teaches him self-control (something she herself lacks), and he is later shown breaking up a fight.
- Garfield and Friends: In one episode, Garfield unwittingly angered a bunch of dogs and tried to discourage them from harming him by telling several lies. One of them was that cats knew karate. It didn't work.
- Garfield's Feline Fantasies featured Garfield fantasizing he was in an adventure movie, including a scene where he and the villain threaten each other:
"Fat Guy": I would like you to meet my associate, Rameet. He doesn't smoke, drink, eat or sleep. He's been trained in the martial arts, you know. Judo, karate, tae kwan do, jujitsu, and machete-eating.
Lance Sterling [Garfield]: Big deal. This is my associate, Slobberjob [Odie]. He doesn't think. He's been trained in macrame, bansai, origami, and he's nearly housebroken.
- Garfield's Feline Fantasies featured Garfield fantasizing he was in an adventure movie, including a scene where he and the villain threaten each other:
- Punkin' Puss and Mushmouse: Mushmouse once practiced Judo with a dummy and then tried to fight Punkin Puss and warned him about knowing judo. However, as Punkin Puss explained after defeating Mushmouse, he wasn't a dummy.
- In the Donkey Kong Jr. segments of Saturday Supercade, when Junior's human partner Bones is cornered by the bad guys he will often claim to know karate in order to try and fight them off; the villains never fall for it and Junior usually saves him before he can do anything.
- In one episode of Johnny Bravo, Johnny goes out with the President's daughter, who later grows tired of Johnny's ignorance of American heritage and calls for two bodyguards to get rid of him. Johnny reacts by stating he's a black belt, but the two guys know at least a dozen forms of martial arts, beat him up, and stuff him in a box under the Pentagon.
- Subverted in Avatar: The Last Airbender when Wan Shi Tong, chasing down Katara and Aang, tells her that Resistance Is Futile, because he is a master of Southern Water Tribe style, Northern Water Tribe style, and even Foggy Swamp style water bending. And then Sokka falls from above, whalloping him in the head with a heavy book.
- In Star vs. the Forces of Evil, what allows Marco Diaz to keep up with Star Butterfly in her adventures is this trope.
Marco: [to monsters] I'm obligated to warn you, I'm a green belt -- with a stripe!
- Generally averted by people who actually seriously practice martial arts, because you wish to defuse not escalate the confrontation. Often the only training for official/licensed mastery, e.g. black belt, is how to avoid getting into fights. Also telling anyone that you know karate is answered by either a "Well you don't look so tough to me" taunt or an impromptu performance of Funny Bruce Lee Noises.