Ringer Ploy

When they're all moving at Kick speed, it's impossible to tell them apart.

There's a bully or bad guy who is making the hero's life miserable.

The hero finally decides to drive the bad guy over the edge. How?

Call in the ringers! They will either enlist friends to wear disguises and costumes that make them look like the beleaguered party, or the beleaguered party will call up their relatives with Uncanny Family Resemblance since they're all indistinguishable from one another.

Once gathered, the hero will use them to overwhelm the bad guy with lookalikes or close-enough-for-horseshoes-alikes. Over and over, Serial Escalation.

Primarily a cartoon trope, though it frequently appears in other media as well.

If the hero must use magic or Applied Phlebotinum to pull off the "many of one person" effect, it's Me's a Crowd. If the hero is cloning himself, it may result in Cloning Blues. If it's a bunch of non-identical-looking people all claiming to be the hero despite having no common appearance, you are looking at I Am Spartacus. Related to Lost in a Crowd. See also Shell Game. Doing this with objects rather than humans is a Needle in a Stack of Needles.

The most common outcomes for the trope are:

The villain never finds out, and the hero thanks his helpers once the villain has left the scene.
The villain finds out and is not happy to have been duped.

Examples of Ringer Ploy include:

Anime and Manga

In an episode of the anime adaptation of Eyeshield 21, this is used to conceal Eyeshield 21's true identity from some delinquents; just as Sena is about to out himself as Eyeshield to save Mamori, a bunch of his fellow Devil Bats show up dressed as Eyeshield, all claiming to be the real one. They all manage to fool them (except Kurita, whose identity is blindingly obvious).

Comic Books

X-Men characters the Stepford Cuckoos are identical sisters who could pull this off if they were ever inclined, particularly as they're gifted telepaths.
Silver Age Superman did this regularly with Superman robots. It became common knowledge that, if the Big S showed up, you couldn't necessarily be sure if you were dealing with the real one at any given moment.
When Minnie the Minx found out she had a fan club made up of girls who dress exactly like her and wanted to be just like her, she taught them everything she knows. This ended up backfiring on her when they spread mass chaos around town and she got all the blame.

Film

¡Three Amigos!. The title characters dress everyone in the village of Santo Poco as themselves to trick and defeat El Guapo.
A brilliant example in the remake of The Thomas Crown Affair. When the titular character returns to the art museum to 'return' a painting he stole, he draws attention in the lobby to his clothes, and then moves into the crowds. First he switches his case with an identically-dressed man's...then four more appear, before the penny finally drops and the security team realises the museum is crawling with men in grey suits and bowler hats. See the whole scene.
Done toward the end of V for Vendetta, with everyone in the city donning capes and Guy Fawkes masks.

Live Action TV

Maid Marian and Her Merry Men had Robin Hood do this with the aid of a Con Artist.
One episode of Power Rangers in Space had the team confuse the Psycho Rangers by having everyone dress up as the Blue Ranger.

Western Animation

Tom and Jerry: Jerry, overwhelmed by bullying Tom sends a distress call out to all his relatives, who all look exactly like him. They are onscreen simultaneously and Tom is freaked out trying to deal with them.
Magilla Gorilla: secondary cartoon character Mushmouse does the same thing with all his identical cousins to confound villain Punkin Puss.
Kick Buttowski: Kick enlists the entire neighborhood to dress up and behave like Kick to confound the neighborhood tattletale. They're all onscreen at the same time doing Kick-related mayhem and Ms. Chickorelli's logic fails when the real Kick emerges from his home, having been cleaning his room the whole time. Cue the unmasking sequence with the neighborhood kids (and some of the adults) taking off Kick helmets.
Played With in My Life as a Teenage Robot: Jenny takes different battle forms to fight Megawatt. At the end she defeats him by having Brad, Wakeman and Tucker dress up as the other battle forms besides the one she's currently using herself.
This trope was a favorite of cartoon creator Tex Avery, who directed both:
- "Tortoise Beats Hare", a Looney Tunes short in which Cecil Turtle calls up all his identical relatives to beat Bugs Bunny in the fabled tortoise-hare race.
- Northwest Hounded Police a Droopy short with the punchline:

Wolf: Say, I wonder if there were more than one of them little guys?
Dozens of Droopys: What do you think, brother?

The same joke was used on a Huckleberry Hound short.
The Batman used it once on Mr. Freeze.
In Avatar: The Last Airbender episode "The Headband," Aang hosts a dance party in a cave for Fire Nation kids. When the headmaster of the school arrives and tries to get Aang in trouble, all the Fire Nation kids gradually put headbands on so that the headmaster is tripped up with ringers for long enough that Aang can leave.