The "Shy Guy Jungle Serial Key" legend is an urban legend revolving around the 2012 role-playing game Paper Mario: Sticker Star.
Description
In World 5-1, Shy Guy Jungle, players can dig around in the giant trash pile to find several discarded items, one of them being a mysterious serial key "XD3R-B8HH-9ZR2-FL16". What exactly this serial number is for is the subject of rumors. It was theorized that it was either a Club Nintendo code or an eShop code, but entering in the key results in the player receiving a "wrong code" message rather than the "code has already been entered" message one would expect had the code already been used. As of yet, no concrete purpose for the code, if it even is one, has been found.