The Ninja costume is a very popular Halloween costume for both grown-ups and kids. It is usually worn by boys but some girls wear it, though technically a female would be a Kunoichi costume. A variation of this costume is the Mortal Kombat Ninja costume from the once widely-popular Mortal Kombat series.
Most ninja costumes consist of the same general design, wearing all black and a mask that only has the eyes visible. Although a Japanese sword called a katana is the most common weapon used for costumes, any other Japanese weapon will also work, such as nunchaku or sais. This design originated from kabuki theater designs as opposed to actual ninja, which instead wore regular clothing to fit in with the common people in the area they were dispatched to.
Sometimes people who do not wish to go out for Halloween may joke facetiously that they were dressed up as a ninja, as a reference to their legendary stealth skill.