missingno

Pokemon Red and Blue, 1996. Talk to a certain old man, fly to a coastal strip, and the game reads the letters of your name as if they were wild encounter data. Land on a slot the game never meant to use and out comes MissingNo, a scrambled block of a sprite that garbles your Hall of Fame and, famously, duplicates whatever item sits sixth in your bag. It is a raw out of bounds read dressed up as a monster. Return the real species, or MissingNo when the index runs off the table.