Origin:
It originated from a guy trying to know how to get the caps in super-mario 64, this is how to get the metal cap in the answers(http://www.gamefaqs.com/…/198074-how-can-i-unlock-all…) then Sarai give the link to a streamer called “LOLYOU” that was read over there, then the link was given to the chat and people found it very amusing and started posting it everywhere.
To get metal cap you need to enter swimming beast star and ride dinosaur to door, not floor switch near door and go left then you will see tunnel to water fall and there is a final switch but water current is strong so be careful and be careful of flying red guy spitting bullet at you