Reptile

From UltimateMK.com

Reptile first appeared as a hidden character in Mortal Kombat for the arcade. He was a green male ninja. Players could fight against him by getting a double flawless and a fatality on The Pit on a round when shadows appeared across the moon. Depending on the revision of Mortal Kombat, the shadows would appear more or less frequently.

In Mortal Kombat, Reptile was a green copy of Scorpion or Sub Zero.

Reptile returned as a green [[Male Ninja (Mortal Kombat II)|male ninja) in Mortal Kombat II. This time he was a regularly selectable character. He is generally considered one of the less capable characters.

Reptile retained a similar appearance and moveset when he appeared in Ultimate Mortal Kombat 3.