Accidental Dance Craze

Let's say Alice is just walking along, and suddenly she gets a horrible itch in the middle of her back. There just happens to be some music playing, and as she contorts her body to try to reach the itch (coincidentally in time with the music), people around her start to do the same thing, thinking it's a dance. It becomes a Dance Sensation, and usually Alice doesn't even notice, as she's still trying to get to the itch.

It often gains momentum when one person in the crowd yells, "Hey, look at those cool dance moves!" or something similar. That person starts doing the move, and pretty soon everybody's doing it.

Overlaps with Squirrels in My Pants, as this is sometimes the reason for the motions.

Film

 * Airplane!, when Elaine is dancing in the tough-guy bar, and the man with the knife in his back points at his back, trying to get someone to help him.
 * The Disney animated film A Goofy Movie featured Goofy improvising his "Perfect [fly fishing] Cast" when he accidentally winds up on stage at a concert. It was adopted and mimicked by the actual performers and became a new dance craze.
 * Also, while visiting the Possum Park attraction, Max gets a possum in his pants and everybody starts clapping like he's dancing.
 * Can't Buy Me Love: nerd Ronald is pretending to be cool and needs to learn the cool dance moves. He sees an educational program about an African Anteater Ritual mistaking it for American Bandstand and picks up a jerky, jumpy dance which he debuts at a school dance. Everybody thinks he's cool so they copy him.
 * The Three Stooges are being trained to be gentlemen, and are assigned a dancing instructor. She tells them this is the latest dance and do exactly as she does. Of course, at the moment the music starts, a bee flies down the back of her dress. They follow her contortions to get rid of the bee, including all of them jumping out the second floor window into a fountain below.

Live Action TV

 * Doctor Who: Eleven is doing this charming flaily sort of thing with his hands over his head at Amy Pond's wedding. It catches on with the kids, and then with everyone else. Official material would later name the dance as "The Drunk Giraffe."
 * In Misfits, the titular offenders end up popping pills that reverse the effects of their powers. Simon, who is normally metaphorically invisible (and literally after the storm), is suddenly incapable of going unnoticed. A woman asks him to dance and Simon, delighted and amazed, takes to the floor. He does these dreamy moves with his arms in front of his face, and before long everyone in the club is doing the same thing.
 * Jeeves and Wooster: Geeky naturalist Gussie Fink-Nottle, having trouble confessing his love to Madeline Bassett, complains to Bertie that male newts have it much easier, as they profess attraction by performing a simple body-shaking movement—which he demonstrates, in the middle of Bertie's club, inspiring a new dance which nearly everyone in the room is doing by the time he and Bertie leave.
 * I Dream of Jeannie: At a party, Jeannie does her 'fold arms, nod head' spell casting gesture. One of the guests sees her, thinks it is a new dance move, and soon everyone at the party is doing it.
 * The Beverly Hillbilles - the Clampetts encounter a group of Beatniks, who are intrigued and ask them what they dig. Jed tells them they dig taters, and pantomimes a shoveling action - 'Diggin' Taters' becomes the Beatnik's new dance of choice.
 * In Twin Peaks, Mr. Palmer shows up at the party for the Icelanders. One of the songs triggers the memory of his daughter and he starts to dance, weeping and clutching at his face. Catherine dances with him to try and avoid a scene, but he keeps clutching at his face. Desperate, she imitates his face-clutching hand waves. The Icelanders, not knowing what's going on, start to mimic the movements.

Music

 * Charlie Brown, sung by Vicky Rosti, is about a young man who's liked and admired wherever he goes. The song mentions as an anecdote one time when Charlie slipped on a banana peel and others copied his moves, creating a new dance.
 * The video to the Crazy Frog song "Crazy Frog in the House" features children following Crazy Frog around town and turning his everyday actions into a dance craze

Western Animation

 * Happens in Doug in the episode "Doug Can't Dance". Doug has to go to the school dance, but he doesn't know how to dance. He spends the episode trying to learn how(and failing). At the end, he goes to the dance, and Roger drops a hammer on Doug's foot. Cue Doug jumping up and down grabbing his foot. Patty then copies him, and the dance craze spreads.
 * Two examples from Phineas and Ferb, both involving animals:
 * Candace's "Squirrels In My Pants" dance from "Comet Kermillian".
 * Jeremy's dance in "Nerdy Dancing", when Ferb (who's secretly controlling Jeremy through a remote-control exoskeleton) starts swatting at a bee.
 * Patrick starts one by being mistaken for the only competitor in a dance competition to not use a partner in one episode of SpongeBob SquarePants.
 * Happened twice in The Flintstones: In one episode Fred stubs his toe and starts hopping up and down. Bystanders join in, and soon everyone is doing "the Frantic"; near the end of the episode, Fred ends up inspiring "the Flintstone Flop" from falling off a table. In another episode, "The Twitch" is created when singer Rock Roll has convulsions as a reaction to his pickled dodo eggs allergy.
 * When Grape Ape stubbed his toe on The Great Grape Ape Show (episode "A Grape is Born"), he started jumping up and down, holding his toe and saying "Oooh, Aaah, Grape Ape, Grape Ape". Not only did nearby buildings get rattled, he also created a new dance.
 * In an episode of Samurai Jack, Jack goes undercover to infiltrate a nightclub with close ties to Aku. When a group of teens start to become suscipious of Jack, he starts busting out his martial arts moves and the teens excitedly copy his actions.
 * Camp Lazlo: Raj creates one while trying swat a mosquito in "Slap Happy". It also happens to be same as the secret handshake of Scoutmaster Lumpus' Brotherhood of Funny Hats.
 * SpongeBob SquarePants: Patrick gets a cramp in the middle of a dance contest, and that sparks off a craze in Bikini Bottom.

Real Life

 * The Italian dance of Tarantella, according to folks, started out when tarantulas bit farmers on the fields. Since the folks thought the spiders' bites were dangerous, they danced until they sweat to drive the venom out. Other people then danced to the beat and the heat, starting a dance frenzy.
 * One of reasons behind this may be that venom of tarantulas from Poecilotheria genus causes both "pins and needles" sensation (which usually is caused by circulation disrupted by bad pose and solved by moving the affected limb more and more), and later random cramps all over the body for a month or so (which can lead to strange contortions when the victim tries to move while in pain and partial paralysis).