Madness Makeover

The Sparkle Sliding Scale of Rationalism Versus Perfectionism (descending)

Much like the Evil Makeover occurs when Alice has her Face Heel Turn, a Madness Makeover occurs when Bob finally snaps. It's often a slow and gradual process, that becomes more and more apparent as his Sanity Slippage goes on.

A common first change is his becoming unkempt or Bob attempting to give himself an Important Haircut. If he doesn't, he'll probably have Messy Hair, at least, in line with the rest of his grooming getting worse. In addition, his eyes may change, either by way of their pupils shrinking or growing, one iris becoming larger than the other, or lines and bags appearing, especially if his madness is caused by (or leads to) sleep deprivation. As Bob's sanity slips, his clothes begin getting dirty and wrinkled, he loses his posture and finally, he begins smiling a Broken Smile, perhaps even starting to recite a Madness Mantra.

Alternatively, the Madness Makeover can take on the Creepy Cleanliness variety. Little by little, the character will start dressing more sharply. Others will dismiss this change in him or her to be S/he Cleans Up Nicely, not knowing that this is a warning sign of their Sanity Slippage until it is too late.

Examples of Madness Makeover include:

Anime and Manga

Soul Eater has a combo example of a Madness and Evil Makeover: Justin Law is revealed to have been the one that murdered BJ and secretly become a disciple of the Kishin. Naturally, his new evil/mad outlook comes with a new evil/mad wardrobe, as all of his previously priestly adornments are replaced with the three-eyes of the Kishin.
- In the anime, Stein slowly starts to go crazy and change his look. He starts by looking more tired, and works his way to forgetting his glasses, wearing his labcoat half-off one shoulder, and walking around hunched over while muttering a Madness Mantra. And he's STILL the most Badass character in the show besides the Physical God Shinigami-sama.
Precia of Magical Girl Lyrical Nanoha. Sane Precia is a kindly smiling woman with hair neatly combed back. Insane Precia is a madly laughing woman prone to pupil shrinkage with unkempt hair that's always covering one of her eyes.
Claire Stanfield from Baccano! is introduced looking innocent and inconspicuous enough (spoiler, folks!) that you might mistake him for completely sane. This, naturally, has to be remedied—so he drenches himself from head to toe in the blood of his victims and alternates his facial expressions between crazy psychotic grins and...well, even more crazy psychotic grins. And that's before he turns on his Glowing Eyes of Doom...
If you were to collect all of the before and after shots of the Higurashi no Naku Koro ni cast, in a few cases, you'd be hard-pressed to believe it was the same character. Shmion's probably the most obvious case, but there are some of Rena that would give them a run for their money.

Comic Books

In The Sandman, Delirium, who used to be Delight, gets one of these, though it's implied in a Flash Back rather than seen in-story. As Delight, she's shown to have normal hair and be wearing nice dresses, but after she changes to Delirium, she has Multicolored Hair, Mismatched Eyes, and a wardrobe that would best be described as eccentric. There's also something of a reverse example (though not necessarily an inversion) when Delirium forces the madness back at one point and her eyes become the same color as a result.
Batman: The origin of Harley Quinn. At the culmination of her being twisted and manipulated by The Joker, she robs a costume shop to get her villain costume, which she promptly dons to break the Joker out of Arkham
Ralph Dibny's appearance in 52 becomes more and more disheveled as his obsession with dark secrets to bring his wife back to life grows stronger. Then, in his final appearance, he is sober and elegant once again and his behavior is professional and heroic.

Film

Happens to Alex in Madagascar as he succumbs to hunger.
The narrator in Fight Club becomes more beat-up and disheveled as the movie progresses, a clue that he actually is crazy.
Interesting example in the horror film May: dowdy, frumpy May becomes stylishly gorgeous as she slips into homicidal madness.
Smeagol in The Lord of The Rings goes from being a Hobbit to a shrivelled, psychotic creature as the One Ring eats away at his sanity.

Literature

In House of Leaves, Johnny doesn't become aware until well into the novel that he is looking more disheveled and crazy the more he obsesses over the manuscript, neglecting himself so much that his teeth start to rot by the end of the book.
Lucy gets all slinky and sensual as she falls under Dracula's spell. Oddly this is not considered an improvement by her faithful suitors.
- Riffed on by Kate Beaton.
Sir Lancelot in Le Mort d'Arthur is so unkempt after running mad from his love for Guinevere that nobody recognizes him.
Sisterhood series by Fern Michaels: Rosemary Hershey started out as beautiful in an artificial way. However, when the pressure, guilt and stress of her crimes come back to haunt her, this trope hits her hard. She ends up looking like something the cat dragged in, looking deranged, and several characters commenting on her dramatic change in appearance.

Live Action TV

The Firefly tie-in series The R. Tam Sessions shows River's descent into insanity while at the Academy. The first "session" shows River as a happy, cheerful girl wearing clean clothes and with well-tended hair. However, as the series progresses, River's hair becomes ragged, tangled and unkempt, her face becomes more twisted and her clothes become a dirty mixture of hospital garb and prison clothes, on top of her steadily more manic and insane mannerisms and dialogue.

Theatre

Older Than Steam: Ophelia famously becomes ungroomed as well as unstrung after Hamlet breaks up with her in Shakespeare's play.

Video Games

In Warcraft 3, Arthas gets both one of these AND an Evil Makeover.
Although SKX (Serial Killer X) from Condemned was never sane, as the game series progresses, his appearance and mannerisms certainly worsen. He goes from looking semi-normal, to shaving off his hair, carving an "X" on his forehead, having half his face shot off, having eyes that would freak most people out, wearing only a blood-stained butcher apron, and at the end of the second game, having a completely mutilated face from wearing Oro mouthgear.

Webcomics

Though it's mostly due to trance-deprivation, Vaarsuvius of The Order of the Stick appears to be getting one of these. Their hair is unkempt, their face is pale and lined with veins, and their robes have grown filthy. Later it gets replaced with Evil Makeover.
When Oasis goes crazy(er) in Sluggy Freelance, she gives herself an Important Haircut (cutting her Anime Hair into shorter, black-dyed mess) and starts carving letters onto her arms with a knife.
Dave in Narbonic.
Jack after his encounter with Zimmy's hallucinations in Gunnerkrigg Court.

Western Animation

Azula in Avatar: The Last Airbender, during the series finale when she has her Villainous Breakdown. By the end, her hair is unkempt, her eyes are lined and baggy, her posture's taken a dive, and she's alternating between Laughing Mad and sobbing.
In the My Little Pony Friendship Is Magic episode "Party of One", when Pinkie Pie starts thinking that all her friends no longer like her or her parties, she goes through the inverse of the hair example mentioned above: her normally poofy mane and tail straighten out completely. (She gets better when she realizes they don't hate her, though.)
- On top of that, her entire body becomes slightly desaturated in color to a more muted, gray-toned pink.
- Fluttershy and Twilight Sparkle also get unintended expressive makeovers in "The Best Night Ever" and "Lesson Zero" respectively (Twilight's is pictured above), and it's played much more straight. More minor examples include Twilight Sparkle in "Swarm of the Century" and Rarity in "Suited for Success". Applejack in "Applebuck Season" is a borderline case, since she never quite snaps, but otherwise plays the trope straight.
- The Return of Harmony plays with this: The further they fall under Discord's influence, the more desaturated each girl becomes altogether - the gray tones are actually shown spreading across them.
- You do not want to see Princess Luna lose her sanity - as demonstrated in The Mare In The Moon, where her Super-Powered Evil Side was the series' first Big Bad.
Fry in Futurama gets one of these during his extended stay in a robot insane asylum, partly due to him actually going insane, partly due to the various "treatments".
Morph of the X-Men animated series was left for dead, and when he returned after a Face Heel Turn, he had deeply sunken in eyes.
Ezekiel from Total Drama World Tour after attempting to stay with the crew after being voted off twice. He slowly starts to go insane—by the time they get to London he has green skin, blood shot eyes, crooked teeth, and a chunk of his ear missing. By the time they get to Africa his clothes are tattered, he has claws and fangs, nearly all his hair is gone, and he acts like an animal.
In The Simpsons episode "Hurricane Neddy", Ned loses it and chews out everyone in town after they mess up on the job of building a new house for him. This is showed by his previously smoothed down hair becoming dishevelled with a few strands falling out of place. He ends up checking himself into a mental hospital.

Real Life

Britney Spears. She publicly shaved herself bald, went to rehab several times, tried to beat a car to death with an umbrella and eventually had to be committed for psychiatric evaluation. She's gotten better since then.
Truth in Television. Going insane rarely helps one function, so "simple" tasks like grooming can become near impossible so a resulting change in appearance is expected. Subverted by those who are pathologically inclined to be neat and "clean". They are hindered instead by the need to be presentable, and will likely have a HBSOD if they get dirt on themselves.