Maybe someone just threw on the first thing they saw, only to find that everyone's asking them where they got their new look. Perhaps one person tells another to wear something they think is hideous in order to sabotage them, only to find that almost everyone (or in even more ridiculous example, literally everyone) is wearing the exact same thing the next day. It could be that someone wears something in order to be different, only to find that everyone wants to copy them, making it look like they're just following the crowd. In any case, someone wasn't trying to make something popular, but they inadvertently do just that. The three types are: Type I -- accidental outfit or character's normal wear becomes fashionable Type II -- spiteful sabotage backfires because the target wears the damaged/switched clothing anyway, and the results becomes fashionable Type III -- attempt to be unique backfires as the styles becomes fashionable Sometimes is used as a Take That to the fashion industry, which is seen as a)following the lead of popular or famous people even when what they are wearing looks ugly or stupid or b) only using its clothing to shock people rather than turn out everyday, normal pieces. Related to Accidental Dance Craze. Type I
- In the film So Fine, the protagonist accidentally creates a fashion trend of wearing pants with the bottom missing.
- A classic urban legend says that when Clark Gable undressed in It Happened One Night, revealing that he wasn't wearing an undershirt, thousands of clothing factory workers lost their jobs due to a drop in demand. Gable's agent made sure he wore and undershirt in his next big screen role, which created demand again.
- In Dexter's Laboratory the titular character starts a 'broken glasses fad' when he cracks the lenses on his own. Later, Mandark shows up with his arm and leg in casts, which the kids are similarly impressed with.
- Shows up twice in Ozy And Millie. Wannabe-cool kid Avery shaves himself after mistaking Ozy's Running Gag fur loss as a new trend to follow (and is more mollified that it was his kid brother Timulty who revealed it). Later, Millie accidentally paints her head black. After cleaning it off, Felicia catches up to her. With a black head. Then a few strips later comes by wearing the same style overalls as Millie. And straightened her wool to be more similar to a regular fox's.
- An episode of Kim Possible had her mission outfit become a fashion trend when she lands on the catwalk of a fashion show
- One segment of Phineas and Ferb have the titular pair make their everyday wear the latest fashion. Ended by a Type I when Dr. Doofenshmirtz paradrops his duplicates into the mall, and his standard attire becomes the next craze. The whole segment was a Take That to the fashion industry.
- There was a Simpsons comic in which the titular family were determined, from their TV viewing styles, to be the typical American family (a frightening thought), which led to their clothing becoming the next omnipresent fashion.
- In Mean Girls, Janis steals one of Regina's shirts and cuts holes in the front where heer breasts are, hoping to embarrass her. Regina puts on the shirt anyway. The next day, everyone at the school is wearing one of these shirts.
- In the old Apple Game Alter Ego, your cousin gives you her tacky hand-me-downs. If you wear them to placate the relatives, and have a high enough score in social graces and calm, you start a local fashion trend.
- In one early episode of Sabrina the Teenage Witch, Sabrina decides to get even with Libby by magically making her wear mismatched knee socks when she tries to mock her Libby responds by asking why Sabrina is still wearing matching socks. A scene later all her Girl Posse is wearing mismatched socks too.
- The girls in John Tucker Must Die attempt to embarrass the titular character by sending him out in public in just a thong. He somehow makes thongs on guys popular.
- I Love Lucy: In the episode Lucy Gets a Paris Gown, Lucy desperately wants a high fashion Jacques Marcel gown. She and Ethel end up with burlap sacks that they think are high fashion because their husbands tell them they are. Combined with Type I, as Jacques Marcel sees them and is inspired by the sacks and ends up designing, well, burlap sacks that he calls high fashion.
- In The Shelters Of Stone a Libby and her Girl Posse give Ayla some clothing to wear to a party, none of which is culturally proper for her: for example, they give her a belt which is for a boy to proclaim he is now mature enough to engage in sex but has not yet done so. (They also attempt to give her a horrible makeup job, but she refuses their "kind" offer.) After she learns of this, she decides to continue to wear the clothes and it becomes something of a fashion to wear them as she does.
- On Lizzie McGuire, Gordo starts to wear 1960s-looking clothing and a hat in order to stand out, but finds that the entire school is copying him.
- In Doug a popular Show Within a Show comes on with a character who has the same Limited Wardrobe as Doug. The other kids think he's following a fashion trend started by that show, despite his protests that he always dressed that way.
- Terry Pratchett's Discworld. The female dwarf Cheery Littlebottom, in attempting to liberate herself from the orthodoxy of unisex clothing for both male and female Dwarfs, inadvertantly sets off a new fashion mode among Dwarf girls who are fed up with having to wear the same clothes as the men. the Disc's first fashion supermodel Jools, who is lucky to enter her trade at the same time that the Disc evolves glossy fashion magazines and womens' mags aimed at airheads.
- After grunge bands like Nirvana and Pearl Jam burst on the mainstream in the early 90s, "grunge" fashion suddenly appeared to commercialize on the pop culture success of the music genre. Which is hilarious when you consider the main quality of so-called "grunge" fashion was to wear what wasn't particularly fashionable at all.
Hello, Unknown Troper. You'll need to get known to lend a hand here.
Three days must pass before this YKTTW is Launchworthy or Discardable