Full-Body Disguise

That is not Dick Clark, that is a Dick Clark rubber mask, with a zipper in the back. When he gets off that TV show, year after year, week after week, systematically lowering the standards of this country, he undoes that zipper and underneath... is a cloven-hooved, horned wolverine.

—Bill Hicks

Sometimes you don't need a full-on Invisibility Cloak. You don't care if people see you, just if they see the real you. And so you don an ensemble that completely obscures your features and possibly even your whole body. This is far more than a simple Wig, Dress, Accent. There isn't anything left of you to make out. The you beneath the suit is effectively invisible.

Any superhero or villain with a full-face mask would be included here, (Harley Quinn's make-up counts—how many people would recognize her without it and her trademark clothing and hairstyle?) but superheros with no mask (Superman) or partial masks (Batman, Robin, Green Arrow) would not.

Contrast Paper-Thin Disguise. Also see Latex Perfection, Black Cloak and Alternate Appearance Aura.

Examples of Full-Body Disguise include:

Anime and Manga

In Code Geass, Zero's outfit completely obscures his physical features; among many other things, one consequence of this is that everyone thinks he's Japanese. This also allows C.C. to take over his identity when he's out of action for a year.
The Mysterious Protector in Magical Girl Lyrical Nanoha A's. What originally appeared to be a man hiding behind a simple face mask turned out to be a full body illusion disguising Gil Graham's Catgirl familiars.
In the Read or Die manga, Paper Master Ridley Wan makes one out of paper to impersonate Yomiko's deceased lover, Donny Nakajima. It's so detailed that she fails to realize he's an imposter until he tells her - after she slept with him.
Lupin III uses these from time to time, often to impersonate women.

Comic Books

Watchmen example: Rorschach's mask.
The Thing wore one of these in the early Fantastic Four comics.
V's ensemble in V for Vendetta, including his famous Guy Fawkes mask. This serves the purpose of hiding the fact that he's hideously scarred, as well as reinforcing that the ideas he represents are more important than the individual.
Spider-Man's full face and body costume counts.
The Iron Man armor could alter voices and made it so that Rhodey replace Tony Stark as Iron Man without anyone really noticing the difference.

Film

Monty Python's The Meaning of Life ends a scene set in the Boer War with an African native warrior appearing on screen, unzipping down the middle, and revealing Terry Gilliam in a tuxedo introducing the next scene.
The Antareans in Cocoon.
The alien lizards in V.
In They Live, aliens transmit a signal that disgueses their true appearance from everyone not wearing a special kind of sunglasses.

Literature

An interesting example occurs in the Philip K. Dick book, A Scanner Darkly. The protagonist is a narc, and when he has to appear in public to give a speech about why Drugs Are Bad, he appears only in a "scramble suit". The suit flashes the features and facial characteristics of thousands of different people at a rate too fast for anyone to discern. As such, anyone wearing it looks like a "vague blur."

"Ladies and gentlemen, a round of applause for the vague blur."

One of the conspirators in Voyage of the Shadowmoon wore a mask at all times, not to hide his identity, but to make his real face unrecognizable so he could slip away from trouble at a moment's notice without anyone realizing it's him.
The Stainless Steel Rat would do this as a matter of routine, as it was the only way to commit crime and get away with it in a society where surveillance was pervasive.
The Invisible Man has Griffon wearing dark glasses and heavy clothes for the first several chapters, concealing his lack of an appearance. May also be a Stealth Pun on the title, since a few characters get confused when he tells them he's "invisible."

Live Action TV

Any Super Sentai or Power Rangers shows that use a Secret Identity.
The early part of season 8 in Charmed
The film adaptation of Battleground, a short story by Stephen King, has The Nameless hitman wearing a mask shaped like a human face for his hits, which obscured his features but (from a distance) would make him appear to be a normal person to any casual witness.
Exaggerated in MANTIS, because the full-body suit of powered armour is pulling double duty as a high-tech mobility aid for its paraplegic creator.

Video Games

This is the entire logic behind the Spy's ability to disguise as a friendly class in Team Fortress 2; even if you're seen, they think they're chasing someone else.
Alex Mercer has the Phlebotinum to do this well beyond Latex Perfection in Prototype.

Web Original

In the Paradise setting, human characters are randomly, permanently changed into Funny Animals (and some are gender-swapped as well). After they change, characters have an illusory full body disguise of their old human selves where normal human beings are concerned (whether they like it or not), especially early on when the "Reality Distortion Field" is stronger. A man who turned into a female bear might look much like his old masculine self, just a little overweight—-which means he will need to continue to dress like a man. Normals literally cannot tell anything has changed; only others changed can see them as they are.

Western Animation

In the Charlie and Lola episode "But I Am An Alligator", Lola wears, for a majority of the episode, a large, dark green alligator costume which covers her entire body, with the exception of her arms and legs. This embarrasses Charlie, as she wears it in public, and the size of the costume makes it difficult for Lola to perform basic tasks such as tieing her shoelaces.
The villains of Sushi Pack occasionally don actual full-body suits, most notably Apex, an invading alien. Oleander, a foodee villain, managed to squeeze her frame into a much skinnier body suit in order to masquerade as a gossip columnist in one episode.
In the My Little Pony Friendship Is Magic episode "Sisterhooves Social", Rarity disguises herself as Applejack by wearing a hat (to hide her horn) and being completely covered in mud.

Real Life

Balaclavas obscure facial features. You can guess what they're used for in crime.
- For those who don't know big words, that's a ski mask.
Ghillie Suits. A sniper's Ghillie suit is essentially a cloak made of foliage. It helps blend the wearer into a forest environment, but also breaks up a person's form and makes their outline difficult to spot.
Criminals sometimes use stocking masks, ski masks and even Halloween masks to hide their identities.
If you're going to pretend to be an old man, remember to think about your hands as well.
- He probably would've gotten away with it if he hadn't shucked the mask midflight. An old man with young hands isn't quite enough to report, but the appearance of a young Asian coinciding with the disappearance of an elderly Caucasian is going to be noticed by those already alerted enough to observe him.