Gusty

Gusties (also erroneously referred to as Blusties ) are long, smiling ghost-like creatures that appear in the Yoshi franchise. They always travel in huge packs, allowing the Yoshis to eat them and get extra eggs. They can be used as stepping stones to reach higher areas. In addition to possibly knocking the baby off Yoshi's back, they can spawn endlessly in some areas.

They appear in levels where the terrain is bumpy and uneven. Gusties are prominently featured in the levels What's Gusty Taste Like? and Gusty Glory.

In Yoshi's New Island, their model has a separate face on each side, likely due to the position of their faces in the artwork coupled with the exact way their transparency works.

In Yoshi's Woolly World, Gusties are made from a spiral of string, which can be eaten by Yoshi to create a yarn ball.

In Yoshi's Crafted World, they have no arms, and are defeated in the usual methods, along with running into the wall.

Super Mario World 2: Yoshi's Island

 * Official Nintendo Player's Guide: If it's a blustery day, you'd better watch out for these gale-riding ghosts both in and out of doors.

Yoshi Touch & Go
(They appear from either side of the screen and fly away in a straight line at a considerable speed. If it appears on the lower screen, block its path with a cloud and then wrap it with a bubble.)
 * Shogakukan guide: 画面の左右どちらかから現れ、かなりのスピードで一直線に飛び去っていく. 下画面に現れたときは、雲で行く手をさえぎってからシャボンで包むとよい.