Fans of the Pokémon series know that every time a entry is released comes out, it is usually is two games instead of just the one title; there are differences between them, but other than both offer pretty much the same experience. For players outside of Japan, two Pokémon games per new entry is the norm.
The very first series of Pokémon titles — originally launched for the Game Boy in the mid 90s — was not the exception; well, except for the fact that in Japan players actually got three games in the form of Pokémon Red, Blue, & Green. Pokémon Green never made it outside of Japan, as it was updated to the Blue version that everyone outside of Japan remembers.
Of course, there is also the Pokémon Yellow: Special Pikachu Edition, but that game wasn't one of the original launch titles, but it is still worth mentioning here for the sake of the article.
As it turns out, it seems that Nintendo and Pokémon series developer Game Freak originally intended for a fourth Pokémon game to be released for the Game Boy, and fans are now convinced that this is the case — as new evidence seems to support that theory.
Initially revealed by Twitter user @DrLavaYT — whose content focuses mainly on lost Pokémon history — the source code for the original Pokémon Blue and Pokémon Yellow: Special Pikachu Edition was recently leaked; revealing a code for Pokémon Pink, which is believed to have been a companion to Pokémon Yellow and would've likely featured a Jigglypuff or Clefairy as the main Pokémon.
The people over at Eurogamer had the chance to interview Dr. Lava, and the information revealed by the source code has been confirmed to be somewhat legitimate, although there is no way to know what this alleged Pokémon Pink would've looked like, or if it would've been Clefairy the starring Pokémon.
Before Pikachu became the mascot of the Pokémon series, the developers had actually intended for it to be Clefairy, although it is also very possible that the Pokémon anime may have had a bigger influence on the starter Pokémon's decision — which would've led to Jigglypuff being the protagonist and not Clefairy.