Bremen Mask
The Bremen Mask is a bird-like mask given to Link by Guru-Guru in Majora's Mask. When used, it makes domestic animals other than cows and horses follow Link, who leads them in a brisk march as Link plays his ocarina. It also makes cucco chicks grow into adults, a feat which has the Bunny Hood as a reward.
The mask appears to be named after a Grimm's Fairy Tale titled "The Bremen Town Musicians" in which a group of animals (a donkey, a dog, a cat and a rooster) decide to leave their masters and become traveling musicians.
It can be used in the fight against the Ikana warriors to confuse them.
Obtaining the Mask
Simply talk to Guru-Guru in the Laundry Pool on the night of Day 1. He will tell you a story, and give you the Bremen Mask as thanks for listening.