Fwoosh

Fwoosh is a cloud that will blow you off Tall Tall Mountain in Super Mario 64. You can't defeat him but you can walk right past him. The mountain wall near him is a portal to a secret slide.

Although Fwoosh (as an enemy) is exclusive to Super Mario 64, a Fwoosh-like creature makes a very small cameo in Mario and Luigi: Partners in Time. The cloud appears to blow away the smoke from the Hydrogush 4000 on Thwomp Volcano after the mountain's eruption is put out.