Keaton Mask

The Keaton Mask resembles the mysterious Keaton and can be found in both and.

Ocarina of Time
In Ocarina of Time you can get it by borrowing it from The Happy Mask Shop after you have given Zelda's Letter to the guard. You can then sell it to the guard which you gave Zelda's letter to.

Majora's Mask
In Majora's Mask you get it by (after 4PM on Day 3) going to The Curiosity Shop Owner in Kafei's place after delivering the Letter to Kafei. Then by standing inside a circle-shaped area of bushes while wearing this mask, like that found in North Clocktown, and then slashing the bushes a Keaton will appear and ask you some questions. If you answer them all correctly, you will get a Heart Container.