Yoyleberry

Yoyleberries are fictional berries that turns consumers metal. It is used to make Yoylecake, Yoylestew, or eaten fresh. It is commonly found in "yoylebushes", which are located in Yoyleland. Though it was mentioned as an ingredient for Yoylecake before in Don't Pierce My Flesh, its official appearance was in Get Digging, when Gelatin, Needle and Puffball went to Yoyleland to collect the berries to make Yoylestew for the contest.

Trivia

 * It is unknown what the side effect is called.