Super Mario World (SNES) - Map screen buddies
One of many classic Mario games that contained hidden features and ideas which were never made a part of their ultimate release was Super Mario World - the game is riddled with secrets and features which were not discovered until many years after the game was actually released, one of these features was the map screen buddies.
It is not known to this day what Nintendo were planning for the impact of these mapscreen buddies to be, all we know is that there were two of them - Blue Jay (a blue bird) and Lakitu. The Blue Jay would fly around Mario on the map screen and follow him wherever he went in Yoshi's Island. Lakitu would join Blue Jay in flying around Mario once he gets to Donut Plains 1. Another SNES era title featuring Lakitu as a constant was Super Mario Kart - could it have been intended that Lakitu would act as some kind of mediator as he did in this title?
The truth is, we'll probably never know what the impact of these map screen buddies would or could have been! see below for a video showing them in action on the map screens.
The map screen buddies were first discovered by a guy named Calcwatch from The Mushroom Kingdom in 2002 - over 11 years since Super Mario Worlds U.S release. Who knows what hidden treasures will be revealed in the years to come.