From the Super Mario Wiki
Skeleton Goonies are skeletal undead versions of Goonies that appear in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi Touch & Go, Yoshi's Island DS, Yoshi's New Island and Yoshi's Woolly World. Unlike normal Goonies, they may not be ridden on, and will lose their wings and fall if this is attempted. They also fall if attacked with an egg. Some carry bombs to drop on Yoshi, similar to regular Goonies, but they never carry green Shy Guys. Oddly enough, they have feathers even though they have skeletal wings.
In Super Mario World 2: Yoshi's Island, even though they had their own level, World 6-1: Scary Skeleton Goonies!, they debuted in the first skiing part of World 5. They also appear in the opening segment of World 6-8: King Bowser's Castle.
They appeared in Yoshi Touch & Go where they behaved like their non-skeletal counterparts, flying in the top screen, sometimes dropping bombs and Shy Guys. Hitting them with an egg rewards a Blue Coin.
They also appear in Yoshi's Island DS and Yoshi's New Island with little to no differences in behavior or physical appearance.
They appear in Yoshi's Woolly World in World 6-7: Kamek's Last-Ditch Fly-By, World 6-8: King Bowser's Castle, and World 6-S: Skeleton Goonies' Lava Lair. Like most other elements in the game, Skeleton Goonies have a woolly appearance.
A flightless variety exists known as the Flightless Skeleton Goonies.
Names in other languages