Cow

Cows appear in various The Legend of Zelda games. They are Hyrule's primary source of milk, and are kept in the land's various farms.

Ocarina of Time
In Ocarina of Time, cows can be found all over Hyrule. Many can be found in various holes and caverns (what business they have there is unknown), but a few are also kept at Lon Lon Ranch, and tended to by Talon and Malon. In this game, a free bottle of milk can be obtained by playing Epona's Song in front of a cow. They will appreciate the song, and give you milk for it. In the Master Quest version, several cows can be found Inside Jabu-Jabu's Belly. These cows serve a rather odd function of being a switch, unlocking doors and dropping treasure chests or items when hit by the Slingshot. This is one of the more bizarre easter eggs in the series.

Link can win his own cow by beating the Obstacle Course record at Lon Lon Ranch. The cow will be delivered to his treehouse and can be found in his room.

Majora's Mask
Cows are also featured in Majora's Mask. They are not as commonly found around Termina as they are in Hyrule, but there are several in Romani Ranch. Much like in Ocarina of Time, Epona's Song can be played to a cow, and they will produce milk to give you for free.

The Minish Cap
Cows serve as a path block, potential Kinstone fuser, and friend to Minish Link. One of the Picori is said to have even battled a cow at Lon Lon Ranch!