4. You can fight a super secret character in Mortal Kombat
Long before the Internet was a thing, word-of-mouth was the only way to spread rumors, and a rumor about Mortal Kombat was making the rounds in gaming circles. It stated that under very specific conditions, the game allowed you to fight a secret character known as Reptile.
Reptile was troublesome to locate. It required players to decrypt hints and perform a double flawless victory. Players eventually found him and beat the legendary Reptile. I really wish games still had secrets like these.