Foos are white cloud-like enemies that appear in New Super Mario Bros. Wii and New Super Mario Bros. U. They produce fog that can obscure the player's view. Foos can be defeated with any kind of attack.
 New Super Mario Bros. Wii
A group of Foos
fire clouds at Mario
New Super Mario Bros. Wii marks Foos' debut appearance. They act much like a Fwoosh from Super Mario 64 and its remake, though Foo's wind only produces fog, and does not blow Mario away. They appear only in World 7-5 as part of the stage's main gimmick.
The fog vanishes after a few seconds, and can be blown away by Spin Jumping or propelling Propeller Mario.
 New Super Mario Bros. U
In New Super Mario Bros. U, Foos only appear in Snaking above Mist Valley, and behave the same as they did previously.