The Hat-in-Hand glitch is a glitch that causes Mario to hold his hat in his hand, as if he was stuck in his putting-on-a-cap animation. When holding objects in this state, the objects' models don't render, which means the HOLP will not update.
The hat in hand glitch is performed by picking up two or more caps in quick succession. The glitch works with duplicated normal caps as well as special caps. During the animation of putting on a cap, the hat appears in Mario's hand. If the animation is interrupted at the very end with picking up another cap, then Mario will not update to having the hat on his head instead of in his hand.
Ending the Glitch
Mario will put his hat back on after any textboxes (except for sign textboxes) or any cutscenes. The hat will also go back onto Mario's head if he leaves the course.
When Mario is holding his hat in his hand, it cannot be stolen by enemies.
While holding his hat, Mario will take damage as if he was not wearing his hat.
The HOLP will not update while Mario is holding his hat in his hand, since the hat is rendered in his hand and consequently the object is not rendered, which is required for updating the HOLP.
Use in Challenges
Where can it be done?
Pannen showed in 2013 the courses in which the hat in hand glitch is possible  (Editor note: I don't know if there are more courses nowadays)
- Bob-omb Battlefield, using the Wing Cap
- Whomp's Fortress, using the Metal Cap
- Jolly Roger Bay, using the Metal Cap
- Big Boo's Haunt, using the Vanish Cap
- Hazy Maze Cave, using the Metal Cap
- Shifting Sand Land, using the Wing Cap
- Dire, Dire Docks, using the Metal Cap
- Snowman's Land (outside the igloo), using a hat clone
- Snowman's Land (inside the igloo), using the Vanish Cap
- Wet-Dry World, using the Vanish Cap
- Tall, Tall Mountain, using a hat clone
- Tower of the Wing Cap, using the Wing Cap
- Vanish Cap under the Moat, using the Vanish Cap
- Cavern of the Metal Cap, using the Metal Cap
- Wing Mario over the Rainbow, using the Wing Cap