Hero's New Clothes
The Hero's New Clothes are clothes that Link has worn in some games. They are apparently "invisible" to certain people. The clothes are based on the fairy tale of The Emperor's New Clothes.
Wind Waker
After finishing the game once you have a choice to play a second quest. During this second quest instead of playing with a green tunic, Link has the chance to play in his Crawfish Pajamas, but apparently he is wearing the "Hero's New Clothes", which are invisible to some people. It is not known whether or not the clothes were real or not. Evidence proves that the clothes were real because people have noticed a change in Link's attire and during the end scene of Wind Waker, while Link is carried of in a bubble, a shape of a hat is seen, and finally, when he awakes in the ocean you can see him wearing a tunic.
Phantom Hourglass
The Hero's New Clothes are the clothes that the Man Of Smiles gives Link the first time he visits him. In the game, the item image is transparent. When taken to trade to [Nyeve]], he says he recognizes and sees the clothes that are just perfect for him. He trades you these clothes for a telescope.