Everyone loves a good secret, and video games are often more than happy to provide on that front. Totally different from every other form of popular media, games allow players to explore virtual environments in order to discover content in a non-linear fashion. Because of this, developers will frequently provide incentives to wander from the beaten path, in the form of secret areas, unlockable characters, and hidden easter eggs.
Because of this however, players can be convinced that certain secrets exist within video games, even when they were never planned on being implemented in the first place. Sometimes there may appear to be 'clues' as to the existence of these secrets within the games themselves, although they're often either red herrings or leftovers from unfinished segments.
These rumours are often spurred on by online discussion over message boards and social media as well, becoming the target of forgeries and hoax screenshots, in order to propagate the rumours even further. From uncatchable creatures to characters that will never be unlocked, these are gaming's greatest secrets that never actually existed!