Keaton Mask

The Keaton's Mask is an item found in both Ocarina of Time and Majora's Mask. The mask's appearance may be a reference to Pikachu, as well as Keatons looking reminiscent of a Kitsune.

Ocarina of Time
In Ocarina of Time the mask is the first mask Link gets in The Happy Mask Shop sidequest. It can be sold to the guard standing outside of the gate to Death Mountain in Kakariko Village for 15 rupees.

Majora's Mask
In Majora's Mask the mask can be used to summon a Keaton. Link need only to stand in any ring of moving bushes, cut one of the bushes down, then stand there until a Keaton appears. He will ask Link three questions. If he gets them all correct, he will be awarded with a Piece of Heart.

Obtaining the Mask
You get the mask by going to The Curiosity Shop Owner in Kafei's place after delivering the Letter to Kafei.