Feather

History:

The Majestic Mushroom Eagle used to soar over the Mushroom Kingdom, preying on Mushroom People and Koopas alike from its high perches in the mountains. Rarely a Cape Feather would fall from their 18-ft wings and these became valuable Items. Using a Cape Feather would give its bearer the ability to fly temporarily. When determining Items for the first Grand Prix, Mario insisted that Feathers make an appearance, although due to their rarity, they have no returned since.

SMK:

Every Item in SMK has appeared in every successive game to date besides the Feather, which is strange, because it was a distinctive, helpful Item. When activated, the Feather would allow a racer to jump high in the air. This could be used to avoid obstacles, or more often the case, allow access to shortcuts and other pathways otherwise inaccessible. It has not appeared outside of the Original game though