Stealth Clothes

Many anime characters seem to think that in order to sneak anywhere, it is necessary to at least tie a handkerchief (known as a tenugui) around one's head, with one set of adjacent corners tied under one's nose and the other two knotted to make it into something like a skullcap. (It looks like a variation on the handkerchief-headgear of Monty Python's "Gumbies".) Many fans throw around theories like "tying the handkerchief under the nose is supposed to help dampen the sound of breathing".

In fact, it is derived from ancient Japanese romantic practices. Young unmarried women were not to be too friendly with young men, and home visits at night were right out! So the young man would wear a handkerchief in the aforementioned manner. That way, if the lady liked the gentleman, she could honestly say that she did not see his face clearly (and if she did not like him, he could be identified easily). Over time, the classically-tied handkerchief became comic shorthand for "Incompetent Sneaky Person".

Sometimes this is supplemented with a full Ninja suit, but many characters think the handkerchief alone is sufficient. It usually isn't (but that probably doesn't stop it working as a Paper Thin Disguise). for an example.

A possible version in the proto-trope stage at the moment may be Solid Snake/John Rambo's long bandana.

For the Western equivalent, see Blatant Burglar. If you're looking for the other kind of Stealth Clothes, try Spy Catsuit.

Anime and Manga

 * In the Pokémon animé, Team Rocket use these a couple of times. And it ALWAYS fools the heroes.
 * Happosai, Genma and Soun use the full ninja-suit variation on several of Happosai's "raids" in Ranma 1/2.
 * In the first film, Akane wore one while sneaking into the room of pickling vats.
 * Ranma himself has worn the mask in at least one manga story.
 * Both Tenchi and Ryoko (at different times) in Tenchi Muyo.
 * During the (first) Hot Springs Episode in Tenchi Muyo! Ryo-Ohki, Nobuyuki put one on before trying to look over the wall.
 * Haru from Katekyo Hitman Reborn has done this on occasion, although she stopped doing it in the manga once the series became a battle manga.
 * Keitaro during one particularly explosive scene in Love Hina.
 * Mai-Otome has Arika explaining that her grandmother taught her that this was the appropriate apparel for when sneaking around. (Her grandma taught her some interesting things.) The others make her take it off.
 * Sakuragi used this in one scene of Slam Dunk early in the first match against Ryonan - he supposedly tries to eavesdrop on Ryonan coach Taoka as he gives instructions to his players.
 * In the manga of El Hazard the Magnificent World, the villain Jinnai explains to one of his Evil Minions that since they're sneaking around, they have to wear "Burglar Clothes." Said minion did not understand how that helped camouflage at all.
 * In Magical Girl Lyrical Nanoha, Shamal dons the traditional western cloak-and-dagger garb of a heavy coat and sunglasses to spy on her charge, which does nothing to prevent the first acquaintance that comes along from recognizing her.
 * In Mahoromatic, Suguru and his grandfather use this to spy on Mahoro and Minawa taking a bath.
 * In Cutey Honey the Live Cutey Honey does this while sneaking around
 * In Cosplay Complex resident Lolicon Jenny wore this combined with a cat's tail when she tried to sneak into the bed of Token Mini Moe Athena-- however she accidentally ended up in bed with the main character's Hot Mom instead... which she did not seem to mind that much.
 * Togano of the Huh-Huh Bros. of Eyeshield 21 wears one as he and Kuroki attempt to run away from the Death March.
 * An integral part of Ebisumaru's clothing in Ganbare Goemon (aka Legend of the Mystical Ninja.)
 * Usago of Sailor Moon once wore this while trying to steal her mother's curtains to make a dress. She got caught.

Videogame

 * Available on Gaia Online, as seen here. It's part of a "Panty Raider" item.
 * It's subtle in 16-bit sprites, but Galuf in Final Fantasy V (old-fashioned guy that he is) wears the handkerchief mask if using the Thief job.
 * In The Legend of Zelda: Spirit Tracks: Teacher wears one when he goes searching for Zelda. He doesn't want to be recognized in order to avoid panicking the citizens.

Other

 * The anime-themed CCG Ani Mayhem acknowledged this trope with the card Sneaking Disguise, which actually DID make the character using it harder to detect.
 * Not just in anime, though: Seth Cohen wears these in the "Model Home" episode of The OC (Season 1).