Bob brags about some skill he possess, or some impressive feat he pulled off in the past. In fact, Bob brags quite a lot about this. Alice may roll her eyes at the time, but she remembers. Because, inevitably, Bob and Alice will find themselves in a situation where success (and possibly survival) utterly depends on that skill Bob has been bragging about. At which point Bob will confess, with great embarrassment, that his original claims were very overstated, if not completely fabricated. However, while Bob's first instinct is to turn tail and run, that is simply not an option: by the time Bob is exposed, Alice's plan is completely past the Point of No Return. Since Bob is the Closest Thing We Got, he has no choice but to attempt to live up to the original boasts.
Naturally, since it's a Million-to-One Chance, Bob does just fine.
See also Crisis Makes Perfect, which also involves Bob coming through when put on the spot with a skill he didn't possess, but differs in when it becomes apparent that he didn't have the skill.
Truth in Television in that "fake it until you make it" is a viable business and political strategy. Understandably though, in Real Life they do all they can to avoid the aforementioned million-to-one chances, preferring bluffing, intimidation and disinformation to avoid actually showing what they're bragging about for as long as possible until they can afford to. Despite this, cases when a hastily-put-together fake manages to produce the required outcome (and even force them to imitate it in the final product as a result) are not unheard of.
- In Eyeshield 21, Hiruma likes to brag that he has a kicker on his team who can score a field goal at 60 yards, over half the field away from the goalpost, calling it the 60 Yard Magnum. Musashi, the kicker, repeatedly refutes the point, saying it's just an intimidation factor (later he says he's never made one from further than 55 yards...which is still an impressively long kick). Then it comes down to the last second in the Christmas Bowl, with Deimon trailing 42 points to 44 and possession on the 50 yard line (for those who don't know, that puts them 60 yards from the goal post because of the 10 yard long end zone). What follows is one of the most beautiful and kick ass scenes in the entire series.
- Hiruma forced Sena into the identity of "Eyeshield 21", the ace running back from Notre Dame High School, so he wouldn't be scouted by other sports teams and Mamori wouldn't flip about him playing such a dangerous sport. As Sena later discovers, the mythos that Hiruma had built around the identity is largely true concerning the real Eyeshield 21 — the latest in a series of running backs to wear that number at Notre Dame. It's revealed in the final chapter that after the World Cup, Sena actually became the real Eyeshield 21 in the US.
- One Piece: While not exactly an example of this trope per se, Usopp's statement and actions after the timeskip during one of the climactic battles shows his boasts now hold a lot more water.
Usopp: It's true, I've deteriorated. I used to lie a lot more...now I can actually do these things!
- And in an odd way, many of the fake stories he told around his home town mirror actual events he would later encounter on his journey. Those stories were still fake, but he'd be able to then truthfully retell them when he returns.
- Superwomen of Eva 2: Lone Heir of Krypton: Asuka often boasted about being the best pilot ever and the greatest fighter against the Angels, but in reality her confidence and her self-esteem were very fragile and she was not sure her skills and training were good enough. However she gradually discovers she has powers she was unaware of, becomes a heroine, and thanks to personal growing she shows she can take down anything and anyone.
- In How Trixie (Somehow) Saves Hearth's Warming, Trixie is Mistaken for Badass by Vixen due to her typical boasting and dragged into saving Heart's Warming from a villain named Leidr who's buried the North Pole in a blizzard. Trixie soon has to actually live up to her boasting when she has to fight and Amarok and the Rat King. While she and Vixen get turned into wooden toys by the Rat King, Trixie ultimately gets properly motivated enough to start a prison break and ultimately defeat the Rat King through trickery and quick thinking. She's quite surprised not only by the fact she beat him, but by the castle full of innocence she freed from him start celebrating her as a hero.
- This wonderful image: http://zombiecarter.deviantart.com/art/Futurama-Undead-Zapp-Brannigan-331944580
- ¡Three Amigos!: Ned mentions that a passing biplane is the same kind that he flew in one of his prior movies. At the end, the other Amigos need him to fly this plane to escape from El Guapo's army. Ned confesses that it was his stunt double who actually flew the plane. They climb aboard the plane anyway, and Ned flies like crazy.
- In Memphis Belle bombardier Val has not exactly gone out of his way to deny that he is almost qualified as a doctor, even if he never specifically claims so. When Danny is wounded during the mission and the others look to Val to save him, he finally fesses up, admitting he only took two weeks of medical school before enlisting. The Captain, Dennis, gives him a speech about how he's the closest thing they got, and he goes off to save Danny's life...
- In Snakes on a Plane, Troy claims to be able to fly a plane, and have logged hundreds of flight hours. And then it turns out that actually, he was talking about a PS2 game, but he manages to land the plane anyway.
- Mystery Men: Mr. Furious supposedly has the superpower of rage-induced super-strength, but, when called on it near the end of the film, he reveals it's all an act. However, when rescuing the Love Interest from the clutches of the Big Bad, he becomes genuinely furious, genuinely gains rage-induced super-strength, and starts kicking ass.
- Chicken Run: Fowler talks constantly about the time he spent in the Royal Air Force. At the end, the chickens expect him to pilot their homemade aircraft to freedom, and he admits that he was in the Air Force as a mascot, not a pilot. He ends up flying anyway. Interestingly, he's not the least bit ashamed at being a mascot, and seems surprised that the others actually expected him to be able to fly a plane. I mean, he IS a chicken. Fortunately, Fowler was observant.
Ginger: Fowler, you have to fly it. You always talk about "back in your day." Well, today is your day.
Bunty: You can do it, you old sausage.
Fowler: (beat, then salutes) Wing Commander T.l.Fowler, reporting for duty.
- The title character of Rango finds himself boasting big about having killed several men with a single bullet and, after accidentally accomplishing the feat, being made sheriff, at which point he has to do it for real.
- A Star Trek: Deep Space Nine novel once featured Sisko bragging about being able to hit a target with a phaser blast using a mirror. Later, that exact situation crops up on the station (with Odo becoming the mirror); Sisko pulls the stunt off but afterwards admits he had exaggerated his ability.
- Ciaphas Cain is constantly on the receiving end of this because of his (partly accidental) status of a Fake Ultimate Hero. The best example probably being in the first novel, when his friend assumed he'd want to sneak into an enemy camp for fun (although he is quite competent he's also an admitted Dirty Coward).
- In the Septimus Heap series, a ghost asks Septimus if he can perform a certain spell and he says "almost"—not because he knows anything about the spell, but because he knows the ghost will get horribly upset if the answer is "no". Of course, later on they need the spell to heal a dragon-boat and they scramble to make it work.
- Breaking Bad is all about this. Walter White creates the persona of 'Heisenberg' both to terrify the criminal underworld he has become embroiled with and to relieve himself of his guilt over the drastic measures he takes. Over time, however, Walter relies more and more on Heisenberg to the point where his mask becomes his true personality, although elements of the well-meaning family man do still reveal themselves to be there. Sadly, however, he eventually becomes unable to interact with even the people most precious to him without relying on Heisenberg, which causes them to become fearful and hateful of him.
- Game of Thrones: Daenerys' title Khaleesi of the Great Grass Sea was more In-Name-Only since her horde was comprised of the pitiful remnants that stayed alongside her after Drogo's death. That is until Season 6, when she really backs it up.
- Star Trek: Deep Space Nine:
- An early episode has a Bajoran, Li Nalas, who is famed as being a great resistance leader, who later admits he is nothing of the sort. It's something of an inversion in this case, in that his reputation was not his own doing (he was, in fact very uncomfortable with it), but actually spread by other Bajoran freedom fighters who needed a hero to inspire them. He did actually kill an infamous villain, but it was mostly a lucky accident (he stumbled upon the guy bathing in a lake, shot him in his underwear when he saw him running to his phaser, and only found who he was after someone else came across them). After that, as his legend grew, he got credit for almost every successful campaign by the resistance despite never having actually been in charge or heavily involved in carrying them out. But when the time comes, he shows that he can be every bit the legend that people already believe. Even after proving himself, Li Nalas shows that he still considers himself unworthy. His Last Words are "Off the hook," reflecting his relief that he'll no longer have to live up to a reputation he doesn't think he deserves.
- The station itself does this over a three-year period. In the pilot episode, Kira uses thoron fields and duranium shadows to try to convince a Cardassian attack force that DS9 has 5000 photon torpedoes and integrated phaser banks, when all it has are six photons and an almost-phaser. Three years later, Sisko warns a Klingon attack force that DS9 has 5000 torpedoes ready to fire, but they assume that he's using the same trick that Kira did. This time, however, it's no bluff, as the ensuing Macross Missile Massacre demonstrates.
- In an episode of Seinfeld, George claimed to be a Marine Biologist to impress a woman. Later, he and that woman were walking along a beach when they came upon a crowd gathered around a beached whale who is having trouble breathing. George removes a golf ball from the whale's blow hole and saves its life.
- Played with in Scrubs. Elliott insists that her brief endocrinology fellowship has made her an expert on the subject, when in reality she's just very good at hiding textbook pages all over the hospital. When Dr. Cox tries to expose her by scheduling her to give a lecture about endocrinology, she panics until JD makes her realize that all her obsessive efforts to hide the fact that she was faking it has led to her becoming a genuine expert on the subject.
- In Once Upon a Time, the Miller's Daughter, Cora, lies to her king (who is nearly bankrupt) that she can spin straw into gold. The bluff backfires on her, as the king promptly orders for her to be locked in a tower and to transform a roomful of straw. Luckily for Cora, though, Rumplestilskin does know how to spin straw into gold, and he's willing to do it for her. Cora demands that he teach her how as well.
- Warhammer Fantasy: Wulfrik was once a tribal chieftain who got drunk at a feast and proclaimed himself the greatest warrior that ever lived and that he'd killed every type of beast in the Chaos Wastes twice, among other things. The Chaos Gods took him at his word, and he soon discovered that he could now speak in all the tongues of men and beasts (and elves, and dwarves, and beastmen, and...) in order to challenge them to prove his boast true. At first he thought this was a curse, before realizing his life was now an unending challenge that could only bring him ever-greater glory.
- Brad Evans of Wild ARMS 2 claims himself as the "Hero of Slayheim" in order to keep the heat off of his friend Billy, the real hero. He proves himself more than capable of carrying the mantle once he regains his confidence, however.
- In Chapter 3: The Paper Hero of Mega Man X: Command Mission, X and Spider go to rescue some POWs inside a prison. There they meet up with a hero in green armor Steel Massimo who in reality is just a random cowardly reploid in the armor of the real one, who has given it to him, before he has been stripped down to practically nothing and hung out to dry. The fake Massimo finds him and cries over him. The real Massimo tells the fake one that he’s glad he gave him his armor, and that he can be a strong fighter if he tries. Massimo begins the game pathetically weak, with average LE but no offensive or defensive strength to speak of...at LEVEL 1. And even at level 1, his LE is close to that of X at level 10.
- Before the start of MediEvil, Dan boasts about being a great hero, and is remembered as one, but really isn't: he was made a knight when his boasts caught the ear of the king. When the Big Bad showed up and threatened the kingdom, however, Dan did step up to lead an army to fight him. And then got killed by the first crossbow bolt fired by Zarok's forces. Whoops! By the end, however, he's truly become the hero he claimed to be. Being undead helped with that.
- Captain Qwark of the Ratchet & Clank series. Throughout the series he boasts about how amazing and heroic he is, but always fails to live up to it (he's even a villain in the first game). In the third game however, he fakes his death, but when Ratchet and Clank find him, Clank tells him that there's still a chance for him "to be the hero he always wanted to be". Cue his entrance during the final boss battle in which he helps you fight Dr. Nefarious.
- He's also helped out in A Crack in Time, despite maintaining his pathetic qualities.
- Invoked in Final Fantasy XIV, in the Miner class questline. Wide Gulley learns that his mining records have been artificially inflated by his father, and his first response is to scramble to actually accomplish those records. The fact that he obviously can't do that doesn't stop him from trying, because he's just that peeved about being given credit he doesn't deserve.
- George Takei's famous "shirtless fencer" scene from the Star Trek: The Original Series episode "The Naked Time" was originally meant to be done with a Japanese sword, but Takei (in addition to wanting to avoid Asian stereotypes) was a big fan of old swashbuckling films of the Errol Flynn type, so he told them he was a skilled fencer to get to use a fencing sword instead. After it was agreed, he immediately took up a fencing class to pull off a good showing.