Link marching with the Bremen Mask while cucco chicks follow him around
The mask can be obtained in the Laundry Pool area of Clock Town, where it's in the hands of Guru-Guru. It originally belonged to a Dog who was leader of an animal troupe. Link receives the mask after listening to Guru-Guru's confession about how he stole it. However, Link needs to listen to Guru-Guru's confession on the night of the First or Second Day, since he and the rest of the Gorman Troupe will flee from the town afterwards. It should be noted that the syllables in the words that Guru-Guru sings during the confession match the beat of the background music, the Song of Storms.
The mask allows Link to play a marching melody, which makes domestic animals other than cows and horses follow Link, who leads them in a brisk march as Link plays his ocarina. The Bremen Mask can be used in the fight against the Ikana warriors to confuse them and make them march along with Link, rendering them vulnerable. 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 Town Musicians of Bremen, in which a group of animals (a donkey, a dog, a cat and a rooster) decide to leave their masters and become traveling musicians.
On the third row of the Mask Subscreen, the Keaton Mask (Fox), the Bremen Mask (Falco), the Bunny Hood (Peppy), Don Gero's Mask (Slippy), and the Mask of Scents (Pigma) are said to represent Starfox characters, implying that Nintendo created the appearance of these masks (save for the Keaton Mask and Bunny Hood, both of which appeared in Ocarina of Time) with the sole purpose of hiding an easter egg in the game itself.
The Japanese occasionally use the prefix お (o) in front of nouns to make them more polite. Most of the masks in Majora's Mask are called お面 (o-men). However, the Bremen mask is known as the ブレー面 (burei-men). ブレー or 無礼 (burei) means "rude". Thus, the name translates to "rude mask", a joke on the fact that it doesn't use the prefix お (o).
↑"Dear guest...Long ago, I was in an animal troupe, with dogs and donkeys and such. Why could a...? Why could a...? Why could a man join?!? That's 'cause a man is an animal, too, my boy! They were all great. But there was one thing I didn't like about it... Why was the...? Why was the...? Why was the dog the leader?!? Was it 'cause something was wrong with me, sir??? Oh, that dog was an amazing leader! He always had a stellar troupe no matter what animals he had to work with..." — Guru-Guru (Majora's Mask)
↑"That's why I...That's why I... That's why I stole it... The dog's mask. I stole it. I wanted it because it was the leader's mask... But I no longer need it... I give it to my guest." — Guru-Guru (Majora's Mask)
↑"The leader was a good instructor. His members matured quickly and they became adults in an instant." — Guru-Guru (Majora's Mask)
↑"I don't really get it, but just seein' these guys with a crest and all... I don't have regrets about anythin' anymore. I'm perfectly satisfied. Here...You can have this from me..." — Grog (Majora's Mask)