As of 2015, none of the characters who appeared in the original "Mortal Kombat" game have been officially retired. However, not all of the 10 playable characters from the first game appear in every subsequent entry in the series.
Of the 10 original "Mortal Kombat" characters, Sub-Zero is the only one to appear in every main game in the series. Scorpion and Liu Kang have appeared in all but one subsequent entry, while Sonya Blade, the only female character in the original game, has appeared in all but two games. "Mortal Kombat X," the most recent entry in the series, features all of the characters in the original cast except for Shang Tsung.