Wishi is one of Yoshi's brothers, and the youngest. He is white, and believes that if you wish upon a star, the next day your wish will come true.
The Secret Yoshi
Wishi appears in Yoshi's Story, where he is unnamed and secret, much like Bishi.
Wishi appears again in Paper Yoshi: Yoshi's Story 2, where he is named.
Wishi appears in Mario Kart J, where his partner is Bishi.