Golden Feathers are a type of powerful, rare feathers that can only be found in the Game Boy Advance remake of Donkey Kong Country 2: Diddy's Kong Quest.
There is a total of forty Golden Feathers throughout the entire game, with one hidden in every level, plus a few additional ones. Golden Feathers are usually either well hidden, or in hard-to-reach spots.
The whole purpose of collecting Golden Feathers is to present them to Cranky Kong, who will be residing in his hut. Diddy and Dixie Kong may then use any Golden Feathers that they've collected on Expresso II to increase his stats, so that Expresso II can partake in Expresso Racing.
Each Golden Feather that is used on Expresso II will increase one stat of the player's choice by one point, either Strength, Speed, Flight, or Boost. Each stat can be upgraded to a total of ten points each, meaning that all forty Golden Feathers must be found to fully power up Expresso II.
Although not many stats need to be upgraded for the early races, the later races will require that almost every Golden Feather in the game be found if Expresso II is to have a fighting chance.