The ninjas Scorpion and Sub-Zero have been present in the Mortal Kombat games since the first installment and return for Mortal Kombat X. A number of other ninja characters have also made recurring appearances in the series.
A number of male ninjas that have a similar appearance to Scorpion and Sub-Zero (but with different coloration) have also become mainstays of the series: Reptile, Ermac, Noob Saibot (given the name Bi-Han in later games), Smoke, Rain, Chameleon, Tremor and Reiko. Female ninjas in the series include Mileena, Kitana, Jade, Khameleon, Tanya, Frost and Skarlet. The similar appearance of many of the game's ninjas stems from the cost and limitations of motion capture in the early titles.