From the Super Mario Wiki
Wendy O. Koopa in Pipe Island.
Pipe Island is the third level of Yoshi's Safari. It is located in the Light Realm of Jewelry Land. As the name implies, Pipe Island is an island covered with pipes. Pipe level is full of Paratroopas, and Nipper Plants. This lush pipe covered land is home to a Boomerang Bro., who acts as a boss. At the end of Pipe Island, Mario and Yoshi encountered Wendy O. Koopa accompanied by a Winged Anvil that would fly back and forth shooting horseshoes. After Mario shoots it in the face with his Super Scope it will fall out of the sky and onto Wendy if she is below it at the time. Being hit by the Anvil three times defeats Wendy. After defeating Wendy Koopa, the duo continued on to the next level, Crescent Coast.