Vanish Cap from Super Mario 64

Vanish Mario.

The Vanish Cap is a transparent red cap which is acquired after hitting a Question Block. After putting the Vanish Cap on, Mario turns temporarily near-invisible, allowing him to run through enemies, meshes barriers and certain types of walls. Invulnerability from enemies is granted alongside this. The Vanish Cap is found in Super Mario 64 in blocks in Jolly Roger Bay, Snowman's Land, Wet-Dry World and Vanish Cap Under the Moat.

In Super Mario 64 DS, Luigi can take on the abilities the Vanish Cap grants, but instead he uses a Power Flower to do so.

In order to obtain the Vanish Cap, go to the bottom floor of the castle and go to the room where there are 2 pillars. Ground Pound on both pillars to lower the water level, allowing you to walk to the moat, which was filled with water. Go to the square hole in the moat to enter Vanish Cap Under The Moat, which obtains the Blue Switch . After you reach the end, jump on the Blue Switch so that you are able to get the Vanish Cap.

The Vanish Cap also appears in Super Mario Odyssey and is unlocked after completing the The Darker Side of the Moon although unlike it's previous appearances, the Vanish Cap will make you completely invisible unlimitedly until you change cap. The suit is purely for aesthetic effect meaning you don't get the special powers (such as being able to walk through mesh walls) when you wear it.