"Reptile only appears in versions 3.0 and 4.0 and can only be fought when playing as either Sonya or Scorpion in version 4.0. His name shows as "Scorpion" but he wears green and can do both Scorpion's spear special move or Sub-Zero's freeze move. He is also extremely difficult to beat." - KLOV
Also, ERMACS are "error macros", which myth explained as a secret hidden character (who would, in fact, appear in later games).