Theiss Titillation Theory

"The sexiness of an outfit is directly proportional to the possibility that a vital piece of it might fall off."

This basic theory underwrites Stripperiffic clothing, Impossibly Cool Clothes, and pretty much anything else you stick female characters into: what makes clothing sexy is the hope of a catastrophic Wardrobe Malfunction. The Trope Namer is William Ware Theiss, costume designer on Star Trek: The Original Series, who first codified the concept.

The theory acknowledges that this possibility is entirely imaginary: the true magic of these outfits is that no matter what She Fu the wearer attempts, she is never ever going to expose a nipple. Not in this time slot. Having said that, the TTT takes advantage of an odd side effect: a particularily sexy outfit actually out-titillates a nude woman. Evidently, she who might become naked is more interesting than she who already is.

Particularly common in Science Fiction and related genres. However in Will and Grace, Debra Messing occasionally wore outfits that would not be anatomically feasible for a better-endowed woman.

Though Theiss was a costume designer, according to Inside Star Trek: The Real Story by Herb Solow and Robert Justman, most of the costumes following this theory were actually somewhat more modest before being "improved" by Gene Roddenberry. According to the Art of Star Trek book, Theiss preferred to design costumes that only appeared to be in danger of slipping or coming off, through the use of strategically-placed sheer or skin-tone fabric.

Impossibly Low Neckline ("What's holding it up?"), Absolute Cleavage and Sideboob ("What's keeping those two strips from slipping off to one side or the other?"), Godiva Hair ("All she has to do is turn her head a little...") and Underboobs ("That shirt should ride up!") are common forms of this.

Theiss was further able (forced?) to add to the effect by the censorship rules of the time in terms of what parts of the body could or could not be shown (the navel being the most well-known restriction). He found he could get a surprisingly erotic effect from the carefully arranged display of areas of skin not generally considered erogenous.

Compare Wardrobe Malfunction.

Contrast Fetish Retardant.

Not to be confused with the Theis Titillation Theory.

Anime and Manga

 * In One Piece there is nothing holding up Boa Hancock's robe except the sheer cruelty of the universe. This is MUCH more apparent in the animated version.
 * And yet Rindou, her bazooka-wielding underling probably has her beat as far as this trope is concerned. Seriously, is her short jacket duct-taped to her nipples or something?
 * Gaap in Umineko no Naku Koro ni wears a dress that appears to have a pretty good-sized strip chopped out of it all the way down and very barely stitched back together with laces. It's been described as "a wardrobe malfunction waiting to happen."
 * In Macross Frontier, Sheryl's stage outfits fit the trope enough. However, this is only an illusion as most of the time she's actually wearing a holographic body suit.
 * Halibel in Bleach wears a tight top exposing gratuitous underboob. Her pants, which barely consist of enough material to cover her inner thigh until just above the knee, are also held up only by a sash. Lilinette's vest also looks pretty malfunction-prone.
 * Though the underboob never popping out is understandable, considering
 * There's also Isane in the Beach Episode.
 * This is played surprisingly in Bleach, considering how Stripperific many of the women's outfits can be. The female characters, despite fighting fairly often, suffer nowhere near as much Clothing Damage as male characters. You might be able to argue that this is because the women don't wear enough clothes to damage.
 * The strangest invocation of this trope has to be in the gag manga Kidou Senshi Gundam-San. Char Aznable says this is why he wears his iconic mask.
 * Liru's magic "top" in Magical Pokaan looks like it would be hard to keep in place even without suspenders pulling down on it.
 * Chocolate Misu's magic suspenders in Sorcerer Hunters.
 * Cowboy Bebop's Faye Valentine. Particularly in the movie, which has a scene with strong rape-y overtones, wherein the one button that appears to be her top's only fixture is sliced away by the Big Bad. Given her figure, this should have resulted in her clothing flying open rather spectacularly. Since it didn't, we must conclude that her breasts are coated with an adhesive; it's the only way that scene makes any sartorial sense. Of course, since it's implied Faye dresses like that to distract people, she may need a certain amount of help keeping it on.
 * Yumi Komagata from Rurouni Kenshin wears a top so low that it should not be physically possible to keep up, and indeed constantly looks like it's about to fall down. Word of God says that he's gotten letters from female fans attempting to Cosplay as Yumi asking how she does it.
 * In one Detective Conan chapter, a woman dressed in what looks like a dress made out of a really long scarf appears. Absolute Cleavage included.
 * Princess Tutu. Princess Kraehe wears a black tutu which looks like it might fall off at any second. Episode 13 of Princess Tutu Abridged even has the cast trying to figure out how it stays up at one point.
 * Getsumen to Heiki Mina has Ootsuki Miina has an Impossibly Low Neckline that her transformation has got to include double sided tape to keep those puppies from popping out.

Comic Books

 * Several female superheroes fall under this. Notable examples include Starfire whose outfit is part lingerie, part bondage gear and Power Girl and her infamous boob window.
 * Dear God, Emma Frost. As a member of the Hellfire Club, her outfit, while skimpy, was believable. (It was white lingerie resembling the kind that anyone could buy at Victoria's Secrets, combined with knee-high boots and a cape.) However, after her Heel Face Turn her outfits got more daring and more improbable in design. One good example was when she first joined the X-Men: her outfit combined Absolute Cleavage and Impossibly Low Neckline, using a few strategically placed scraps of fabric to form a reverse "X" with her exposed skin. Of course, the lingerie was a dress code for the Hellfire Club, but being  the type of person she is, quitting the Club actually gave her a chance to be more daring.
 * Exactly how Vampirella keeps her costume from falling off is a mystery. Wizard magazine claimed that for Real Life models who dress as the character at conventions, they use aerosol spray glue.

Film

 * Return of the Jedi. Was there any more to Leia's dancing-girl costume beneath the panels of cloth hanging from front and back of the waistline? According to Carrie Fisher on the DVD commentary, there wasn't, and at times, crews standing behind her could see "all the way to Florida", as it were. Oola suffers a wardrobe malfunction as she is being dragged towards Jabba the Hutt, and again as she falls through the trap door. You can still see a short bit of the first malfunction in the current special edition. Older editions have longer scenes.
 * Hammer Horror movies in particular lived with this trope. Women in form-fitting see-through nightwear that could slip off their smooth shoulders at any moment.
 * Subverted in the live-action Vampirella movie. Unsurprisingly, a realistic version of the iconic costume tended to fall off a lot, and they had to switch to a more practical design. The original can still be seen in some promotional material.

Literature

 * Vetinari mentions this in Terry Pratchett's Jingo. "Curiously, the purpose of the nautch girl or exotic dancer has always been less to reveal and more to suggest the imminence of revelation."
 * All over the place in Piers Anthony works—Anthony is fond of having some characters go completely clothed, others go completely nude, and a third group go partially clothed. The first two groups are seen as more-or-less nonsexual, but the third is a major turn on.

Live Action TV

 * One of the best examples of it at work is Theiss' own creation in the Star Trek episode "What Are Little Girls Made Of?" In that episode, a female android named Andrea has a costume the upper portion of which is merely two crossing strips of material. Off the set, public modeled displays of this costume never failed to get a dramatically appreciative reception from at least the men.
 * In William Shatner's Get A Life, he tells a story about how Gene Roddenberry talked that same outfit into a fashion show at a Sci-Fi con. According to one of the people there, the model apparently had to spend the evening "beating men off with a stick". Notable is the fact that Star Trek hadn't even aired yet.
 * According to Herb Solow and Robert Justman's book on Star Trek, William Shatner couldn't stop hitting on Sherry Jackson, the actress playing Andrea, once he saw her in the outfit. Further, the first public modeled display of the costume was in Desilu Studios' lunch room, where Ms. Jackson entered in said outfit—according to Herb, forks stopped midway to people's mouths.
 * Similarly, the top part of the Greco-Roman-style outfit worn by Leslie Parrish (playing Lieutenant Carolyn Palamas) in "Who Mourns For Adonais?" consisted of a single swath of cloth draped across her breasts and slung over her shoulder. Most people who were there believed that nothing held it in place except its own weight, and were absolutely certain it was going to fall off at any second. Parrish, on the other hand, knew that it was stuck to her skin via massive amounts of two-way tape which had torn off chunks of skin during the original fitting; this is why she instead wore a bathrobe during all rehearsals, even the dress rehearsal.
 * In "Mudd's Women," Maggie Thrett, playing the character of Ruth, suffered repeated wardrobe malfunctions during shooting—apparently one of her, ahem, assets refused to remain covered. (Unsurprisingly, the final version of the costume was another of Roddenberry's "improvements.") The ruined shot was saved for a Gag Reel, however.
 * In a male example, one scene in an episode of White Collar had Neal Caffrey wearing nothing but some very low-riding sleep pants, with a waistband that looked very loose. You could practically hear the fangirls pleading for him to bend just a little further...
 * With the amount of bouncing and jumping around Elvira, Mistress of the Dark does, it's a wonder her boobs never fell out of her dress.
 * That's because she's a master (mistress?) of suspense.

Music Videos

 * Lady Gaga usually wears skin-tight clothing, bypassing this trope; but in the video for Poker Face, one of her outfits is a criss-crossing number obviously inspired by the Star Trek Trope Codifier.
 * Kylie Minogue's video for Can't Get You Out Of My Head features a stunning outfit that must be just about to fall off. A still image can be seen here. Apparently there was a lot of double-sided tape involved.

Tabletop Games

 * In the D&D 3.5 edition Player's Handbook, all of the female examples shown in the races chapter have clothing that looks almost exactly like the example pictured at the top of the page. Not to mention the Nymph in the Monster Manual, the Elemental Savant in Complete Arcane, for that matter just about any female character pictured in any D&D book.
 * A noteable exception being the iconic 3.5 rogue, the halfling Lidda, who's typically fully clothed from her neck to her toes. On the other hand, that clothing tends to be skintight, so...

Video Games

 * The entirety of the female cast of Soul Calibur—with the possible exception of Hilde—are participants in this trope, thanks to the implementation of female-focused clothing damage in Soul Calibur IV. In addition to, you know, the huge quantities of cleavage and the rather unusual designs that were carried on from earlier games.
 * Yoshino "Haru" Harusawa of Shin Megami Tensei: Devil Survivor wears an outfit that would do Theiss proud. Looking at her sprites, it's a wonder she isn't having a wardrobe malfunction every few seconds. Needless to say she's a popular character.
 * Specifically, she wears what would normally be a form-fitting dress, except that it's at least two cup sizes too big for her. This makes the top half hang off dangerously low.
 * It doesn't help that she's constantly fiddling with the straps.
 * And you know how significant that is when all the character animations are expressed in a few sprites. That's right; out of say, five sprites they drew of Haru, one of them is of her fiddling with the straps.
 * The Angel: Her newest design from Strange Journey and Devil Summoner can be described as so: a light chained blue scarf that barely covers the breasts and nothing else.
 * Gaia Online--
 * Ruby is wearing what appears to be a strategically-tied bedsheet with no bra. The jury's out on whether it's being held up by her rack or by the sheer force of her hotness.
 * Sam. They don't make cover-alls in her size.
 * Pretty much the entire cast of Disgaea: Hour of Darkness, males included. The archers are only kept decent by the camera angles.
 * Dead or Alive Extreme Beach Volleyball: Unrealistic clothing physics are the only thing that keep this from being an H-game.
 * This would probably explain the immense popularity of Sunspear armor and Kurzick armor among Guild Wars's Elementalists and Ritualists, respectively.
 * Morrigan's robes in Dragon Age. There are more Stripperiffic examples, but the loose fit, the cleavage and Sideboob indicating lack of a bra, make it look like she could escape her top during any of her magical gestures.
 * Mai in Fatal Fury/King of Fighters. Her outfit looks designed to fall off.

Western Animation

 * This is parodied in an episode of The Simpsons, when it's Agnes Skinner who wears a skintight dress to Homer's award ceremony as "Man of the Hour". Homer's father, her co-host, asks, "What's holding that dress together?", to which Sideshow Mel stands and answers, "The collective will of everyone in this room!".

Real Life

 * This is the idea behind the "fan dance" and "bubble dance" invented by the famous burlesque dancer, Sally Rand.
 * Gypsy Rose Lee's burlesque routines famously didn't reveal much skin; her signature move was sliding her shoulder strap off her shoulder.
 * Soooo many red-carpet dresses, it's not even funny. Whether it be see-through or the slow edging of a nipslip, you know that the more TTT a dress is, the more likely that's what's gonna be leading on TMZ that night.
 * In Brazil, this trope is invoked for strapless dresses/bikinis, being usually called "Tomara-que-caia" ("I-hope-it-falls-off").
 * Paris Hilton is well known for wearing outfits like this for the cameras.