The Teenage Mutant Ninja turtle costume (known as Teenage Mutant Hero Turtles in Europe and Tortuga Ninja in Spanish-speaking countries) is a very popular costume for Halloween, based on the various comic series by Peter Laird and Kevin Eastman and the subsequent television shows and movies. It is has been considered a major piece of American popular culture since 1987 and the costumes are usually worn by boys.
There are enough Ninja Turtle characters and designs that nobody will need to be left out in small groups. Not only are there the four turtle brothers - Leonardo, Donatello, Raphael, and Michaelangelo - in their color-coded bandanna style, but also the comic version where they all wear red bandannas. Other TMNT turtle characters can also be added to the mix, including Slash, Tokka, the female Venus de Milo, or the mechanical Metalhead. Someone can even go dressed up as their sensei, Master Splinter.
Because Ninja Turtles are a common theme for Halloween costumes, those dressing up may wish to differentiate themselves from the rest. Luckily this is easy enough to do, as the turtles have worn various costumes throughout the toy line, the comics, and the cartoons.