Cape Feather

Cape Feathers are power-ups in the Super Mario Bros. series, first appearing in Super Mario World. When collected, they usually give the player a cape that allows the player to fly around and glide, as well as a spin attack.

Super Mario 64 Manifestation
Cape Feathers can be found in some personalized copies of Super Mario 64, despite not being in standard copies. They function similarly to the Wing Cap, though usually also allows the player to do a spin attack with the cape, similarly to it's functionality in Super Mario World.

Cape Feathers usually appear in levels that usually have the Wing Cap, such as Bob-omb Battlefield and Shifting Sand Land. Due to the Cape Feather's similarities to the Wing Cap, there is usually no edits to the levels it is found in except for the Cape Feather's appearance.

It is theorized that the Cape Feather is a remnant of Super Mario FX, which would have supposedly been very similar to Super Mario World. It is currently unknown if this is true, or if the Cape Feather appearing is just a coincidence.

Trivia

 * In Super Mario 64 DS, the Wing Cap is obtained from a feather, potentially being a reference to the Cape Feather.