The rumors I remember from my childhood:
~A kid who said if you mailed your Pokemon game to a person, when it returned, you could travel to a new island that had a fat nurse joy and a Pokemon that doesn't faint other Pokemon, but kills them by devouring their souls.
~In Super Mario 64, if you got 100 coins, Mario would pick his nose. Also, in addition to Bowser, there were Bowser family members who had their own unique boss battles. In one battle, the Bowser family are doing a line dance and you have to trip them doing the crouch attack move. Also, a weird fight against a Baby Bowser where you make him cry before Mama Bowser jumps in.