From the Super Mario Wiki
Windbags are brown, eggplant-like enemies that spew strong winds from Yoshi's Island DS. The strong wind blows four Nipper Spores out of the Nipper Dandelion, which eventually land and become Nipper Plants. If egged, they will die, but a few seconds later, they will regenerate. Yoshi will bounce off it if he touches it, and it will faint for a bit.