Players eventually noticed that the green ninja only appeared for a fight on the stage appropriately named The Pit. They also eventually figured out that he only appeared after players went unharmed in both rounds without blocking and when they finished their opponent with a fatality. To further complicate matters, the green ninja only showed up if silhouettes flew in front of the moon in the background during both matches. The silhouettes appeared roughly once every five or so battles, so it was entirely possible for a player to do everything right and still miss out on the green ninja fight.
Every once in a while, a red ninja would show up in place of his green counterpart, convincing MK fans that they'd accidentally fulfilled some other mysterious set of requirements. In reality, the red ninja was the product of a completely random graphics error. During maintenance, Mortal Kombat arcade cabinet screens displayed a log of win streaks, encounters with Reptile the green ninja, and other secret information. The same log kept track of ERMACS, which increased each time a player encountered the red ninja. ERMACS was short for ERROR MACROS, referring to bugs like color palette errors, but Mortal Kombat fans swiftly adopted it as the red ninja's name. Public interest in Ermac eventually reached the Midway Games developers, who rewarded the fans many years later by making Ermac an official character in Ultimate Mortal Kombat III.
The gaming public's love for Ermac was echoed by Pokémon fans' adoration of their own accidental character. The premise of Pokémon is spelled out in the "Gotta Catch'em All" tagline: There are a lot of cute little creatures and you haven't succeeded until you've captured, traded, and leveled up each and every one of them. This mindset is directly reinforced with the in-game Pokédex, the cartoon's Pokérap, and the release of two variations of the same game with their own exclusive Pokémon. The entire world revolved around this concept of completion, but one Pokémon challenged even the most dedicated trainers: Missingno.