Stutter Stop

A character has a stutter or a stammer, and it affects how he communicates with others... badly. But then, usually at some key dramatic moment, his stammer disappears and he is able to speak with surprisingly smooth and eloquent diction.

This is often Truth in Television, as many stutterers don't stutter at all if they're acting, singing, or talking about something they know well.

See also Stuttering Into Eloquence, Porky Pig Pronunciation and Delusions of Eloquence. Can overlap with Out-of-Character is Serious Business if other characters consider their unhindered speech unusual.

Comic Books

 * In The Sandman, Abel never stutters when he is telling someone a story.

Fan Works

 * Up until her early twenties, Kaitlyn Hutchins of Undocumented Features suffered from a severe stutter. Like many real-world performers, it went away when she sang; it also tended to minimize when she was around people she was close to (and vanished completely with her lovers and with one deeply-beloved family friend).  It also vanished when she went full-bore samurai on someone.

Film

 * Shakespeare in Love, where Wabash can barely speak because of his stammer, and is only included in the play because Phillip Henslowe (the "producer") owes him money. But, after a brief false start, he delivers Romeo and Juliet's prologue with perfect eloquence.
 * Subverted in Pan's Labyrinth: the Big Bad tells his stuttering prisoner that he will let him go if he can speak without a stutter. The man tries, fails, so gets tortured and executed.
 * Michael Palin's character K-k-k-Ken in A Fish Called Wanda has a terrible stutter throughout the movie. It vanishes when he gets his revenge on Otto, his major adversary, at the end of the movie. Final credits reveal he now works as an MC at Sea World.
 * In an earlier scene, Jamie Lee Curtis' character kisses him while to get some information out of him, leaving him ironically un-tongue-tied for a few moments afterwards.
 * Palin actually did quite a bit of research on how stuttering works in real life and incorporated it into his performance. Ken's stutter is not as bad when he's around peeople he's comfortable with (Wanda and George), and becomes worse when Otto (whom he can't stand and is scared of) is around.
 * In the John Wayne film The Cowboys, one of the boys on the cattle drive wasn't able to warn them of danger due to a stuttering problem. Wil Anderson (Wayne's character) proceeds to give him a brutal tongue-lashing, and the boy stutteringly calls Anderson a "s-s-s-s-s-son-uh-uh-uh-of-a-buh-buh-bitch". Anderson then continues to antagonize the boy until the youth explodes into a verbal tirade of completely stutter-free profanity. Anderson then calmly congratulates him on getting over his stutter, and warns the boy to not get used to cursing at him like that. The boy never stutters once for the rest of the film.
 * Billy in One Flew Over the Cuckoo's Nest, after he has sex with Mac's girlfriend, but before Nurse Rachet threatens to tell his mother.
 * King George VI ("Bertie") in The King's Speech spends most of the movie stammering terribly, but his therapist Lionel Logue finds that he doesn't stammer when he's very angry and/or swearing.

Literature

 * Used for The Reveal in the first Harry Potter book. The villain was p-p-p-poor s-s-stuttering Professor Quirrell all along.
 * Bill Denbrough from Stephen King's IT. Both Richie Tozier and Beverly Marsh remark on the fact that "Stuttering Bill doesn't realize that he doesn't, always".
 * In Isaac Asimov's short story "Galley Slave", sociology professor Simon Ninheimer stuttered almost all the way through to the end, where he gives a eloquent speech of the evils of AI proofreaders.
 * Simon has a stutter throughout most of the Discworld novel Equal Rites, but loses it after a run-in with some Cosmic Horrors.
 * Erast Fandorin has a stutter/verbal tic that goes away when he's in disguise/in more Let's Get Dangerous moments.

Live-Action TV

 * Lieutenant Reginald Barclay in Star Trek: The Next Generation and Star Trek: Voyager had a few scenes like this. It was usually evidence that he was really certain about what he was saying, but just couldn't get the words out. It wasn't nervousness that caused his stammer, it was his utter comprehension of the danger of the situation they were in.
 * Although on some occasions it was evidence he'd been hit by the Negative Space Wedgie and was Not Himself.
 * Happens at least once to the title character in the TV version of I, Claudius.
 * The title character of I, Claudius eventually trains himself so that he largely loses his stutter. What makes it fit this well is that he had achieved this well before most people thought he had... and so right up until becoming Roman Emperor, he's still seen as poor, stupid, stuttering C-C-C-Claudius. Soon after, he drops the Obfuscating Stupidity, much to his enemies' dismay.
 * A character on Joan of Arcadia had a terrible stuttering problem, made worse by the fact that he was on the Debate Team. So how did he find his voice? Joan discovers that he has an exceptional talent for finding/gathering evidence and arranging excellent presentations.

Music
"Everybody's sayin' that the Scatman stutters But doesn't ever stutter when he sings. But what you don't know I'm gonna tell you right now, That the stutter and the scat is the same thing."
 * Country music singer Mel Tillis has a terrible stutter. Until he sings, that is. This is even the premise for a joke, where someone says that after Mel was having trouble informing someone that they were in danger, someone else told him to just sing it.
 * Tillis was one of the innumerable celebrities to star in Cannonball Run. He actually has to sing some of his lines just to get them out.
 * World famous scat singer Scatman John states in his song "Scatman" that the reason why he sounds so good singing and has trouble stuttering off stage is because he's actually stuttering in his songs. Take a listen.

Theater

 * In the French farce A Flea in Her Ear, one of the characters has something wrong with his palette that makes him stutter. At one point in the play, he gets a prosthesis, and so the stops stuttering at that point. It gets knocked out afterward though and he goes back to stuttering.

Real Life

 * James Earl Jones has a stutter that is present whenever he is speaking extemporaneously without time to prepare what he is going to say. It is never present when he is performing, unless the character he is playing is specifically designated as a stutterer.
 * Rowan Atkinson has a stutter that he overcomes on screen by over-pronouncing certain letters, most notably his Bs.