In Battle RoyaleKiriyama copies Hiroki's martial arts (which took years to learn) just by watching for a few moments. Also, despite being absent often in the novel, he has the highest grades in the class, somehow.
In Ginga Nagareboshi Gin, it supposedly takes years for the wolves to master a single Battouga. This doesn't prevent the dogs from learning them by just seeing them used in battle (usually against themselves) and then using them just as effectively. Taken to extremes by Gin, who learns three of these moves this way, one from a battle he only watched from the sidelines.
Goku in Dragon Ball and the other Saiyans to lesser extent. Roshi took almost a century to master the Kamehameha wave, Goku picks it up by seeing Roshi do it once. Similarly Goku picks up Tien's Solar Flare technique simply because Tien's used it twice on him. However, it's averted with learning how to fly, which requires a timeskip and Krillin figuring it out before he does.
Tien explicitly has the ability to pick up and master other people's techniques by studying them briefly, while Cell and Buu can both master any technique known by someone whom they absorbed.
Taken to extremes with Goten and Trunks: who somehow master the Super Saiyan transformation before they even hit puberty, whereas their fathers spent months or years training in deep space under extreme conditions to learn it.
Even more than that, they skipped several requirements of achieving the transformation, such as experiencing a moment of pure rage. Handwaved later with the explanation that hybrids are able to access the transformations more readily at the cost of lower overall enhancement from said transformation.
Averted with Captain Ginyu, who was extremely weak after performing a Body Switch with Goku. He began to get the hang of Goku's body rather quickly, however, but just how far it would have gone is unknown.
Vegeta seems to instantly learn to sense people by their ki energy (as opposed to needing a scouter to detect them) between his defeat in the Saiyan Saga and his return in the Frieza Saga. Since this isn't even something that can even be "observed" at all, apparently he instantly learned to do it simply by being told it was possible.
Gundam usually averts this, but Kamille Bidan strangely manages to have impressive piloting skills his first time in combat in contrast to Amuro, who couldn't do anything except be Char's punching bag. Although he won a junior MS competition, they use mini mobile suits for that, so it doesn't explain how he can pilot an experimental combat model without any training. Of course the fact he's a Newtype helps, but then again Amuro, had no idea what to do when he first climbed in a MS even with psychic powers.
Invoked in Mobile Suit Gundam Unicorn: hand-carried mobile suit equipment have device drivers (which makes sense). When Banagher first gets his hands on a beamgatling gun intended for the Kshatriya, the Federation-built Unicorn automatically ports the Neo-Zeon weapon's driver to make it usable (though the process takes a few minutes), after which it works perfectly. Might be justified in that chances are, both sides' MS software was supplied by Anaheim Electronics (who are known to be perfectly willing to supply both sides with supertech if they themselves get left alone and more importantly, get paid).
The back stories of Mobile Suit Gundam 00 tell that Union Ace PilotGraham Aker is also this: When he was test-piloting the Union Flag (then in its initial testing stages), he managed to make it transform at high speeds, after having read the instructions once. Thus, the maneuver itself garnered the nickname "Graham Special" thanks to him.
Zig-zags in Naruto, where the eponymous character, despite being an idiot with little natural talent, is able to pick up highly advanced techniques in a very short time through a cloning technique. By creating a thousand or so clones of himself, he trains a thousand times faster. Even with that, most of his moves aren't perfected, he just gets better at working around the drawbacks caused by imperfection.
That cloning technique is itself an advanced technique, and almost no one is able to use it on the same scale that Naruto does. He learned at the age of 12 by reading a scroll for a couple of hours. So much of not having natural talent.
One perfect example of this at work was when he first used the Kyuubi's purified chakra. He immediately sensed a hidden enemy, chased him down when he fled, and managed to land a devastating blow without, all faster than could be perceived by trained shinobi. The only problem is he broke his leg in the process because he's not used to the power.
Another perfect example? Well we have one genius in his twenties. He graduated the ninja academy before he was 10. He's incredibly strong, fast as sound, and throughout part I, is regarded as THE strongest character in the series, rivaled only by the Kyuubi himself. On the other hand, we have a 12-year-old brat who barely graduated the ninja academy after three straight failures. He is terrible at concentration, is known as a village prankster, and for a time was considered the "Dead last" of his team. So, the 24-year-old genius invents an awesome jutsu. The problem is, it takes him three-and-a-half years to fully create it. Years later, the 12-year-old idiot hears of the technique, and learns it in a week. HOW IS THIS POSSIBLE!? Granted, inventing a technique is more complicated than learning it after somebody else did the work of creating it, but in a week?
Sasuke managed this after developing the Mangekyo Sharingan. In a single battle he managed to seamlessly combine its offensive and defensive ability into a single ability. Unfortunately for Sasuke, his overconfidence in his abilities nearly got him killed, and his overuse of them nearly left him blind.
Sasuke, and anyone else with the Sharingan, has instant learning of new techniques as a basic ability. So long as they're physically capable of performing it (meaning that they've got enough chakra, and it doesn't require a bloodline trait or elemental affinity that they lack), simply watching a technique once is enough to copy it.
Averted in Super Dimension Fortress Macross. After Falling into the Cockpit, the young hotshot pilot prodigy proceeds to fall over repeatedly and cause extensive property damage. A crash course by a pilot who's actually qualified in operating robots keeps him from bumping into things, but only after signing up for the army and undergoing combat training does he become competent.
Similarly in Neon Genesis Evangelion, Shinji gets browbeaten into the cockpit of Unit-01 and sent against the Monster of the Week... and promptly falls on his face before getting beaten like a red-haired stepchild until the 'mech' takes over.
Somewhat subverted in Macross Frontier, where the main character gets punched in the face and kicked out of the hangar for wanting to repeat his no-training Falling into the Cockpit experience when a mission alert goes up.
Ichigo, from Bleach, goes from rank novice to one of the strongest fighters in the universe, able to go toe-to-toe with shinigami captains and take out lieutenants without even using his sword, after two Training from Hell sessions which collectively comprise about twelve days.
Ichigo's very transformation into a Shinigami (or Soul Reaper) is a perfect example of this. He becomes a shinigami in one quick instance, and immediately knows how to wield, summon, and swing his huge Zangpakuto. And when his Quincy powers are unlocked, he's instantly able to use Blut Vene sufficiently to block a killing strike by Yhwach.
Like with many other tropes, Excel♥Saga parodies this when Excel's bowling training from Nabeshin is over in a matter of seconds, leaving Excel capable of scoring strikes while simultaneously knocking her opponents' balls out of their alleys. Lampshaded when Nabeshin notes there's nothing more he can teach her, whereupon Excel complains, "That wasn't even five seconds!"
Whenever Shirou uses Projection to replicate a weapon, he will instantly gain all experience of battles the weapon itself has gone through, allowing him to wield it (or, depending on interpretation, for it to wield itself with his body following its lead) with ease as if he were a complete master.
Projection itself. Not only is he an instant expert literally better than anyone at it in the entire world, he's even doing it in a form that should be more difficult. And he learns enough to project a perfect Noble Phantasm in less than two weeks. His projection is so good that some of it actually breaks the rules of magic and doesn't disappear, which is apparently almost one of the True Magics. Naturally, he's unconsciously cheating like crazy to do it but...
The Saber and Rider classes have the passive Riding skill, which allows the user to ride any mount or vehicle (with limitations in the cases of some exotic or unique mounts—say, dragons) with perfect mastery.
Similar to Saito from Zero no Tsukaima below, from the prequel Fate/zero comes Servant Berserker (Lancelot) who, thanks to the skill Knight of Honor, can turn anything even remotely usable as a weapon as his Noble Phantasm and use them to their fullest extent, even better than Shirou and his Projection magic. This ability brings to mind one of the tales with Lancelot winning a duel armed with only a twig of wood. Combined with his "Eternal Arms Mastership" he turns out to be a serious combatant who only loses due to a sudden loss of mana supply — and all this in spite of being insane the whole time.
Both subverted and played straight in Code Geass. All the characters who are said to be exceptional pilots are either career soldiers or rebels with experience from the School of Hard Knocks. Especially noticeable is the main character who, despite using a Humongous Mecha as a Mundane Utility annually, is actually one of the worst pilots among the main cast, a fact which the show's creators seem proud of. Made especially ironic in that his late mother was a nigh-legendary pilot back when the Humongous Mecha were still new.
It's also played with in the case of Lelouch's Geass; upon receiving it, he instantly knows that he can command people to do anything by looking them in the eye, but he finds out a couple of its limitations by accident, and then experiments at length to find out the others.
Subverted when one of the main character's Pokémon evolves: in later series, they tend to istantly learn a new move after the evolution, like Ash's Krookodile istantly learning Dragon Claw after evolution.
Kintaro Oe of Golden Boy can master complex skills overnight, through nothing more than insane determination.
Sesshomaru, from InuYasha, being Sesshomaru, is stated in his official character profile to be able to use any weapon to its full potential as shown in the manga by his ability to understand weapon attacks even when he's not touching the weapon itself. He even uses Hiraikotsu perfectly on one occasion. The only sword he struggles to master is Tenseiga because mastering it requires compassion rather than sword skill. This is especially noticable when Tenseiga gains the Meidou Zangetsuha technique. He masters the control and activation of the attack instantly but struggles to increase the attack's strength and potential because doing so requires compassion not skill. Then soon after regaining his original arm he also gains a new original sword Bakusaiga, a weapon that does the polar opposite of Tenseiga.
Averted in One Piece, where Devil Fruit users often have at least some difficulty figuring out what their powers are, and often take a great deal of time figuring out how to use them to full effect. After over ten years for Luffy and over twenty for Robin, the both of them are still learning new ways to utilize their abilities.
Also there are Kaku and Califa, two agents of CP9 who were given their Devil Fruits hours (if that) before going into combat against the Straw Hats. Califa in particular, while they should have had barely enough time to grasp the basics of their powers (Giraffe-transformation and strength sapping soap bubbles respectively), is shown to be quite proficient when she faces Sanji and Nami. Kaku flounders a bit more, though, coming up with ideas and attacks on the spot in the course of his fight with Zoro.
In Luffy's case, it took him a while to even manage to throw a punch properly after eating his Devil Fruit.
Saito from Zero no Tsukaima gained this as his power of a familiar. He instantly understands how a given weapon works and how to use it, and also gains a considerable boost in speed, endurance and strength when using a weapon. There is just one condition that must be met: the weapon must have been created for combat. For example, a sword that was created as a decoration won't trigger Saito's powers. Also it can be any weapon, from a simple sword to a fighter plane or artillery cannon.
Claymore has a disturbing subversion. Clare tries to learn the Quicksword skill and after several days is told she is mentally incapable of ever mastering it. But her teacher has nothing left to live for and cuts off her own arm so Clare can use it.
Adam Blade in NEEDLESS has the power to learn any Needless ability simply by encountering it. Handwaved in that his power is the ability to memorize other powers.
Blade cannot perform the abilities of Needless who have their bodies and minds particularly settled to their powers, this includes Eve, Saten, Riru Roukakuji and other Missing-Links Needless as well; Adam Arclight on the other hand can and has surpassed Blade's Zero power, his own being Positive Feedback Zero, as he can copy ANYTHING.
Memorably averted in Slam Dunk. Hanamichi Sakuragi is The Fool and does have enormous potential, but not only does he have no idea of how to use it, his sempai and teammates treat him like the rookie he is and he's stuck for a long time learning the basics.
Kurapika from Hunter × Hunter learns the basics of Nen in a few months, and is then able to go toe to toe with, and eventually kill Ubogin and later kidnaps Chrollo. Both are members are the Genei Ryodan, and very accomplished fighters and Nen users. Kurapika's designed some of his powers to work strictly on Genei Ryodan and no one else, on pain of his own death. If he'd been fighting anyone else of similar experience, he would have gotten his tail kicked. Even with fighting Genei Ryodan, it still takes a toll on his body.
Ku Fei in Mahou Sensei Negima! notes that in a mere few hours Negi reached a level of martial arts mastery that would take normal people months. He also learned instant movement after two separate training sessions. Not even training from hell. It is explicitly noted that his specialty is really rapid learning and improvising rather than extreme power, however. Another example is Asuna instantly grasping the kanka technique while Takamichi had to work seriously hard at it. As in, spent years at it.
In Prince of Tennis, the main character Ryoma Echizen is shown to be easily copying and mastering techniques such as the snake, Rising Shot, Zero-Shiki Drop Shot, etc., while constantly employing new techniques such as the single-footed split step. However, it's explained that this is because he was trained at a very young age by his father, not because of any natural talent.
Played straight in the Prince of Billiards episode, where Ryoma somehow managed to not only copy everyone else's techniques, but also beat the resident billiards genius. All despite never having played billiards before and committing two fouls in his first two hits.
Averted to an extent in Soul Eater. Maka, Black Star and their Weapons are shown to take some time to get used to new powers/techniques, although in the meantime they do make do with a less refined version. Shadow Star didn't last very long to begin with and was dangerous, and Demon Hunter served its purpose when it first turned up, but Maka only really put it into practice in the fight with Arachne. And between the two she's shown talking with Ox about possibilities for her new technique, which is a nice touch. Demon Hunter's predecessor, Witch Hunter, turns up with less fuss than it did initially.
Ui Hirasawa from K-On! is implied to be one. Episode 12 of Season 1 revealed that she was the one that taught Yui how to read guitar sheets, implying that she learned to play the guitar so she could help her sister learn how to play the guitar, which she does very well when she pulled her Twin Switch. In Season 2, when she, Azusa and Jun went to play at batting cages, she overhears a father give his son baseball tips... and hits a home-run immediately after.
Yuki Nagato is assumed to be one, since she has a direct link to something that is basically a god of knowledge and intellect.
Haruhi: Yuki was really good with that guitar! I wonder when she learned? Kyon:[thinking] Probably the second you asked her...
The espers are a variant. They all just woke up one morning with their powers, knowing how to use them, what to use them for, and that Haruhi Suzumiya was responsible. You can understand why some of them theorize that she might be God.
Invoked in the Digimon franchise. Whenever a Digimon digivolves for the first time, they instantly know the name of their new form, as well as all of their new attacks, and have no problems getting to grips with them.
In Vividred Operation, The girls immediately know how to use their abilities, and they know how to summon and use their weapons by just taking a glimpse at some schematics. That "docking" thing at least takes a flashback sequence to work properly.
The antagonists of Part II of Jojos Bizarre Adventure, the Pillar Men, are the remnants of a race of superhumans who are able to learn new things very quickly. The first Pillar Man, Santana, is able to grasp the basics of modern language after overhearing a few conversations and immediately figures out how to disassemble a machine gun all after waking up from a 4,000 year hibernation. The other three Pillar Men are even stronger and smarter than Santana and can converse normally using modern language after overhearing a few words.
In Girls und Panzer, Team Anglerfish brings Mako into their tank during their first battle, and after Hana (who was initially their driver) passes out, Mako takes the controls and, after looking at the manual, learns how to drive better than Hana almost instantly. Interestingly enough, her quick learning causes her to have trouble trying to tutor others in driving, such as the volleyball team in the anime or Sodoko in the manga.
Katanagatari: Nanami is an unparalleled prodigy capable of learning any technique after seeing it once, and mastering it after seeing it twice. She never learned the family fighting style because her father was too afraid of what she'd be like if she did (and then she learned it anyway). She goes from a powerless waif to the strongest in Japan after she kills her way across the country, gaining the powers of everyone she killed. Unfortunately, she's also a) an antagonist, meaning the hero has to fight her, and b) a Death Seeker, meaning she's trying desperately to die in battle, but is so superhumanly tough that she can't lose a fight.
Taskmaster, in the Marvel Universe, can instantly learn how to do any physical skill or martial arts maneuver his body is physiologically capable of surviving simply by watching anyone else do it once, either live or via recorded media. Handwaved away by explicitly giving him the superpower of "photographic reflexes," or the ability to instantly learn by watching. His most recent mini-series also gave him the more conventional form of photographic memory in addition to his superpower, further enhancing his rapid learning abilities. He also has Awesomeness by Analysis in that he understands what he learns so thoroughly that he can teach other people how to do it.
The whole thing worked against him, however, when he tried to use it on Deadpool, who is just too unpredictable. He even started dancing partway through the fight with Taskmaster, just because.
Similarly, Prometheus, a supervillain of the DC Universe, has a helmet with some fancy technology where he can just pop in a disc with whatever skill or knowledge he needs. This can range from the blueprints for a space station to the skills of the top thirty martial artists in the world—with which he handily defeated Batman.
Once. The rematch was far more humiliating... and that was while it still was a hand-to-hand fight, before Prometheus pulled a gun and then Batman triggered the logic bomb he'd hidden in Prometheus' helmet software: he replaces Prometheus's nervous and muscular systems with the physical characteristics of one man: Stephen Hawking.
Reed Richards of the Fantastic Four does this as part of his suite of Super Intelligence powers. In one instance taking a piece of previously unknown alien tech that transmitted information by smell and rigging a device that translated it... into a video... in ten minutes... after saying that he wasn't confident in his ability to do the job.
A character from The Tick comics, Oedipus Ashley Stevens, is a bored rich girl who becomes one of the world's greatest ninjas... after training for "nearly two weeks!"
Black Alice from The DCU can temporarily steal the magical powers of any spellcaster she can think of, and is shown to be pretty proficient with their powers with no prior experience. At one point she stole power from two spell casters at once. She even stole the powers of the Spectre. Crosses over with Power Copying. She was nerfed to hell and back in the Reign In Hell event but has made a comeback in Secret Six, where it turns out the trope has been subverted... she attempted to use Raven's healing magic to cure her father's asthma, but screwed up and accidentally gave him cancer.
The second Mr. Terrific Michael Holt from The DCU. It's not an explicit metahuman power — he just has a natural talent for learning. Before he became a superhero, he had 14 PH.D's on top of being a gold medal winning Olympic decathlete.
Batman does this, occasionally in-frame, but constantly by implication. Advanced use of computers, forensic chemistry, multiple martial arts disciplines, stunt driving, acrobatics, marksmanship with a variety of ranged weapons (firearm, thrown and otherwise)... all these are barely scratching the surface of the immense collection of formal training and acquired skills Mr Wayne apparently acquired by the time he was 30. Consider that he didn't even start seriously training for anything except CEO-hood until after his parents were killed when he was 8, and that some of the skills he's obtained would normally take even an exceptionally talented real-world student more than 20 years of dedicated training to learn, individually, to Batman's degree of proficiency. And don't forget that, the entire time he was doing all this learning, his training had to compete for his time with nocturnal crimefighting, running a major corporation, cooking the books so that anyone receiving a Wayne Enterprises stock report wouldn't immediately know his secret identity, designing tons of cool, but distinctively branded, toys, jumping through hoops to purchase such toys in ways that wouldn't immediately give away the identity of the purchaser of the world's entire supply of Batarangs, and all of this while maintaining enough of a carefree social life to maintain his cover identity.
Invoked in Steelgrip Starkey And The All-Purpose Power Tool. The tool can be programmed to perform any construction task, using "technalchemy" to instantly form and synthesize new components out of thin air, yet Steelgrip can control all of its features with the precision and skill of an expert. The tool has an unspecified mental link to its operator, and the controls and instruments it creates are in construction forms that Starkey would be familiar with.
In With Strings Attached, as soon as John opens himself up to the Kansael, he knows how to use it and its water powers perfectly—as opposed to the others, who all have a learning curve with their magic (especially Paul). That's because the Kansael is semi-sentient and grants him complete control.
Also, he did fly the first time he jumped off a cliff, but Varx noted that when he transformed him into a Winged Humanoid, he made sure to give him the requisite instincts to be able to fly.
In the Twilight Princess fanfic The Golden Power, Link is revealed to have always had an instinctive knowledge of weaponry, allowing him to adapt and use any weapon he comes across. The fic calls such a person a "Blademaster".
In A Growing Affection, Madara uses his Susano-o power to download decades on ninja training into civilians' brains in a matter of hours. Slightly subverted in that afterwards it takes them a few weeks or even months for their bodies to get up to speed.
Witches in the afterlife setting of Resonance Days tend to be this for any skills relating to their original monstrous form, despite being wiped of their memories. For instance, Oktavia, who had an orchestra-themed labyrinth, can play nearly any instrument within seconds of picking it up.
Deconstructed in Reflections Of Demons where Sasuke almost dies from trying to perform Kage Bunshin no Jutsu via Power Copying with his Sharingan. Zabuza explains that while his Sharingan shows him HOW to perform the jutsu, he doesn't have the knowledge of the mechanics behind it or the amount of chakra required so it can backfire on him.
May be a case of knowing more than he lets on instead, but the Cloud Cuckoolander "swami" character in the Steve Martin film All of Me is "accompanying" a saxophonist on the piano, by occasionally playing a single note with one finger (the same note almost every time, with one exception, where he appears inordinately pleased that the new note fits into the chord progression properly). As the saxophonist finishes up the intro, the swami looks bemusedly at the rest of the keyboard, places both hands on the keys, and launches into a rather sophisticated passage bridging to the main song.
The enslaved humans from Battlefield Earth. Despite never having worked with any technology at all, they quickly become expert pilots, due to a "teaching machine" which beams information straight into the user's brain.
In Demolition Man, cryogenically frozen prisoners can have information implanted into their minds. Simon Phoenix/ Wesley Snipes is implanted with martial arts styles and a password that help him escape, while John Spartan/ Sylvester Stallone is implanted with knitting skills. And is still badass, of course.
John Spartan: I come out of cryo-prison and I'm Betsy fucking Ross.
In Deep Rising, the ship's owner, Simon Canton, knows facts about the sea monster attacking them for no apparent reason.
Well, not quite. He was only guessing as to what the creature was. And at the end, turns out he wasn't quite right either. He assumed that the tentacle-like creatures were individuals from a family of deep sea worms known as Ottoia. In the end, it turns out the creatures were actual tentacles attached to a monstrous cephalopod-like creature.
Lampooned mercilessly in the "We Need A Montage" sequence of the film Team America: World Police, where the protagonist Gary goes from being a talented actor to a talented actor capable of performing at Special Forces levels with any or all weapons and his bare hands... in about ten minutes of real time. But hey, he had a really cool montage sequence, complete with 80s-style power ballad, so why not?
Daniel-san, of The Karate Kid fame, manages to go from dweeb to a Force To Be Reckoned With in the space of a few weeks, with some yardwork thrown in. To the point of being able to defeat Cobra Kai dojo and Johnny who had far longer training. Although Daniel does learn exceptionally quick, this is treated more that Mr. Miyagi was teaching him a superior discipline than what the Cobra guys were taught. This is reflected in the way the fight scenes were choreographed, others moved faster and more aggressively but Daniel behaved more efficiently.
Justified in The Matrix, where all humans spend most of their lives plugged into a computer network through which they receive simulated experiences anyway — their Unusual User Interfaces can also act as Upgrade Artifacts, making it a trivial matter to have a full training regimen for anything from martial arts to piloting written directly into your brain in a matter of seconds. Whether this carries over to the real world is up in the air, though the series' only real-world fight scene is considerably less flashy than all of the other action scenes.
Many characters in various Star Wars media. This is usually explained as due to their Force-sensitivity.
Luke becomes a Jedi in the unspecified period of time it takes the Millennium Falcon to reach Bespin sans hyperdrive. It takes only a few minutes of screen time and no indication is given of extreme time passing. Although real Jedi apparently started training in early childhood, Luke is able to put up a good fight against Vader and use powers such as force jump by the time he leaves the planet. By Return of the Jedi, Luke, who's otherwise spent most of his time looking for Han rather than training, is now a full-blown Jedi, being able to employ mind tricks and numerous other Jedi powers with little effort. He's also a far better swordsman, able to defeat Vader this time.
Paploo the Ewok in Return of the Jedi gets the basics of speeder bike operation instantly, despite coming from a stone-age culture and being too short to reach most of the controls.
Madison from the movie Splash was able to learn English in a single afternoon simply by watching TV. Granted, she's a mermaid with magical powers, but this does seem a bit of a Handwave.
The protagonists of Zombie Apocalypse movies seem to become Instant Expert at any weapon they pick up. But that may just be adapting as a survival mechanism.
In the film The Meteor Man, anyone with meteor powers can temporarily absorb all the information in a book just by touching it. Apparently, they can also apply it, considering that at one point the protagonist acquires martial arts skills from touching a book on the subject. And immediately afterward? Runway modeling.
The Last Samurai has Tom Cruise's character, Nathan Algren. He was built up as a quick study at linguistics and warfare, and before being captured by a Samurai group he was already intensely studying their ways. However, in the course of one winter (three months) that he stays with them, he picks up enough Japanese to carry a conversation. He also becomes proficient with the katana, but he was already shown to be a badass fighter with various other weapons.
In Push Nick has been telekinetic all his life, but sucks as the film opens because he never practices. It doesn't really take him very long to become quite adept at it, and he starts kicking ass once he confronts Carter and Victor.
Troy and Gabriella in High School Musical, despite neither being a trained singer, manage harmony and perfect pitch with a song playing on a karaoke machine.
And highlighted at the end of HSM2 where Troy is told to learn a new song, literally two minutes before going on and after goggling for a moment tells Ryan "I can't learn a new song." Of course, when he goes on stage two minutes later, he's not only learned a new song, but learned how to harmonise with his absent partner.
In The Fifth Element, Leeloo (a cloned human-alien-hybrid-thing) learns English in the space of about a day. She does this by speed-reading the 23rd century equivalent of the Encyclopedia Britannica.
Averted in the first Spider-Man movie, where Peter has to learn to use his spiderweb (and gets hit quite a bit for it). Though his technique isn't terribly graceful the first time out, by the middle of the film he can web-sling his way across town with ease.
Col. Rhodes from Iron Man 2 is immediately adept at piloting his stolen suit, which is in direct contrast to the slow, awkward process of mastering the controls Tony Stark went through in the first film - and he designed the damn thing.
Not to mention, Obadiah Stane in the first Iron Man mastering his Iron Monger suit instantly.
Then there's Tony himself, who makes every other inventor even in the Marvel universe look like morons in comparison. He seems to be able to know the ins and outs of any piece of tech he encounters and even fix problems in that tech that has eluded everybody else for years if not decades even if he's never seen it before or if it's not actually pure tech. One example in Iron Man 3 would be Extremus, a compound designed to cause regeneration in life forms including limbs with major issues that Tony fixes most of within 5 minutes of seeing it the first time despite the fact that he had no indications of knowing anything about biology up to that point.
Avatar, so much. Jake goes running out the door as soon as he physically can, while Norm is still doing motor skill tests. And that's only the beginning: Jake learns to speak the native language, ride a direhouse, ride a Giant Flyer, archery on the Giant Flyer, and rally the Na'vi people against Quaritch all inside 3 months.
In Wreck-It Ralph, Vanellope picks up racing very quickly for someone who never drove a cart before. This was because she was coded to be a racer but was forced to forget how. When she repeatedly says "racing is in my code", she was right.
Francoeur from A Monster in Paris literally has a guitar drop into his lap and is left alone in a room to experiment with it, without any instruction. By the time Lucille comes back his playing is so good, her aunt mistakes him for an incoming talent and includes him in the show. Bonus points because this is basically his first day of existence.
Averted by most Kryptonians and Superman in terms of learning powers in Man of Steel. Clark spends 30 years learning how to control his abilities and has a significant advantage over the Kryptonian soldiers who only seem to have access to Super Strength and Super Speed. Played straight by Zod who, after what seems like no more than a few days of practice on Earth, discovers his full power-set.
Additionally, from what we can see of Clark, it is highly unlikely that he's ever so much as thrown a punch before his first fight with Zod's minions. Nevertheless, on his very first outing he fights like, well, Superman. It's noted that he's not as good in a fist fight as Zod's minions, but he's still able to hold his own against multiple trained super-powered warriors at close quarters.
Parodied in Better Off Dead: "Go that way, really fast. When something gets in your way, turn."
He also manages to write a fourteen-page epic poem about his experiences up to the point where he's getting trained by the elves. In an hour and a half. In a language that a few months ago he only knew a couple of words of (although since then he had been learning every day while living among people who speak it as their main language, which is Truth in Television as far as that effect goes for learning real languages).
Eragon learning magic, considering that we are told that most Riders are years into their training before they are even told that they can do magic, although it is both acknowledged as exceptional in-universe, while also not being unheard of, just rare, since the normal method for training magic users involves forcing them to attempt physically impossible tasks, causing them to eventually unconsciously use magic to perform it. It's also notable that doing so leaves him unable to walk from exhaustion after the first time, and once the instinctual moment has passed, he was unable to so much as levitate a pebble until he learned to use it consciously, this being far closer to how magic users are generally trained.
The Ancient Language itself is an interesting case. On the one hand, it does seem that Eragon learns it awfully fast. On the other hand, it is a magical language. In the third book, a Muggle who doesn't know the language and by all rights should hear nothing more than gibberish, complains that the words ring in his ears longer than they should. And understands his true name when it is spoken to his face. The magical nature of the Ancient Language might cause the words to stick in a person's mind easier.
The most obvious example of this trope would be when Eragon breaks his right arm, forcing him to learn to use a sword with his left. Normally, this is extraordinarily difficult; try writing for a long time or perform some other complex task with only your non-preferred hand. You probably aren't even holding the object correctly, as all your actions must now be mirrored from what you normally do, which works against the natural habits of your brain. Learning to sword-fight with your 'wrong' hand *can* be done, but your non-preferred hand will never be as strong as your preferred, which is why most swordsman never bothered. Not only does Eragon learn to use his left hand to sword fight in a few weeks, he is apparently totally equal to Murtagh, who has been learning to use a blade his entire life and fights Eragon with his preferred hand.
Memoirs of a Geisha revolves around this trope, deconstructing it at one point: The protagonist explains that, due to a wager made between her legal guardian and her teacher, she wasn't given much time to actually practice certain skills. Instead, she would visualize them constantly, study when her mind was most pliable and invented a plethora of mnemonic devices to help her, because there was absolutely no other way for her to achieve her goals and change her situation. She explains that while it looked to others like she was mastering her skills without ever practicing, in truth her mind was working on little else.
Lord Hong of Interesting Times regularly masters in a matter of weeks disciplines that require other human beings a lifetime of study. Everyone else's problem is that they just don't focus.
Subverted in Vernor Vinge's novel Rainbows End, where JITT (Just-in-Time Training) allows anyone to become an Instant Expert in anything, but with the added complication of "JITT-stick," which essentially turns the character into a semi-permanent idiot savant in the area they received JITT in. JITT-stick plays a significant role in the novel's conclusion.
Kellhus from Second Apocalypse does this a lot, as he is the super-intelligent result of a megalomaniacal breeding program. That's why he can do things like become fluent in a foreign language in a matter of days.
In the second Sword of Truth book, the protagonist learns the "dance with death" using the titular blade. The sword apparently stores all the sword fighting skills of anyone who's ever wielded it, and Richard is able to download the knowledge into himself, to the point where he can slaughter garrisons of trained soldiers even without the magic blade.
Becoming an instant expert in more or less anything that takes their fancy is one of the advantages of the transhuman Luculenti in John Meaney's To Hold Infinity. Many taught themselves to paint or dance at the level of the masters of those arts on Earth... as hobbies, taking them perhaps a month or two of practice alongside their normal day jobs.
Another science fiction story invoking this trope is Galactic Odyssey by Keith Laumer, in which the protagonist is put to work sorting indistinguishable glorm-bulbs... which turns out to give him the ability to learn essentially anything with a single run-through.
The wielders of the famous BFS in the Redwall series can all pretty much do it instantly, even though they're mostly aged about twelve and may not ever have picked up a sword before. It's heavily implied that they're the reincarnations of the Sword's first bearer, Martin, and the skills carry over between lifetimes.
Peter F Hamilton's The Night's Dawn Trilogy thrives on this. Everyone with neural nanonics can partake of 'Didactic Learning', which basically embeds any knowledge they might need. They might not be quite as good as someone who's been doing it for years, but they can certainly operate complex objects or understand the local phlebotinum competently. It has basically abolished school. If only we had this tech.
Subverted in the Isaac Asimov short story Profession. Nearly everyone, on reaching their majority, gets an instant education implanted into their brains for the occupation that they are best suited for, based on aptitude testing. There is a downside to this, though: people who receive their education this way become incapable of much in the way of original thought. Only a selected few, with the aptitude to learn the hard, old-fashioned way, are capable of developing new technologies.
Left Behind takes place after all the 'good' Christians have been taken from the earth, and follows a group of people who converted to Christianity after witnessing this explicit miracle. And who talk, think and behave like those 'good' Christians instantly after their conversion. Justified in the case of Bruce, who was a pastor before all this and just lacked proper faith. Not at all justified in case of Buck, who can quote Bible passages, uses unusual lingo, and starts considering holding hands with his new girlfriend to be taboo after knowing each other for just a few weeks. This man is supposed to be a 30 year old sophisticated high-profile journalist who never cared about religion before. While this is likely due to Creator Provincialism, the authors probably wouldn't object to the message that all those rules they live their lives by follow naturally if you just accept Christ in the proper way.
There's also at least once where somebody calls them out on not behaving like "good Christians". See, there was this guy who was pretending to be Christian and running a scam on them. They figure it out and do a reverse-con on him. His friend (who really is a Christian) makes it up to the scammer, saying something like "Yeah, he was planning on cheating you, but he's not a Christian and you are. You're supposed to be better than him." Apparently he got a double-dose of the Instant Expert ability.
In the Semper Fi, the first novel in W.E.B. Griffin's The Corps series, Malcolm "Pick" Pickering's flight instructor nearly brings him up on charges after his orientation flight, as Pick is so comfortable in the cockpit (and is able to easily fly and land the aircraft) that it implies that he lied when he wrote "none" in the previous flight experience box on his application.
In the Old Kingdom books, Sabriel's father, the previous Abhorsen, only let her read one page of The Book of the Dead at a time, ever, spaced out over careful intervals to prevent her from going mad from the information, because that book contains Things Man Was Not Meant to Know. Along comes Lirael some years later. She polishes off the entire Book of the Dead in one night. And when she officially takes up the mantle of Abhorsen, she's instantly proficient at it (though, granted, she's had some years of practice fighting Free Magic nasties).
In the Star Wars Expanded Universe, this is explicitly one of Luke Skywalker's abilities, extrapolating out from the movies. After all, he was able to deflect blaster bolts he couldn't even see within minutes of practicing with a lightsaber for the first time. Combined with the authorial tendency to give him New Powers as the Plot Demands, he can be a very Showy Invincible Hero. Though if you are rebuilding the Jedi Order after having had no more than a few months' training, it doesn't hurt to be a quick study.
Lampshaded in Outcast when Luke goes to learn a technique from the Baran Do Sages, one allowing him to produce and control a low level electromagnetic charge in his own body. Since he's the highly experienced exiled Grand Master of the Jedi Order, not a sage-in-training, he's put through the accelerated course, without ritual or training artifacts. All the same, it takes thirty seconds for him to produce a charge - since he knows a vaguely similar technique - and his teacher dryly says, "Well, that's about eight weeks of apprentice training bypassed." Now he has to learn to control it, which is the tricky part. Luke then asks how long it took his nephew to learn to control his charge, and was told three days. Luke smiles.
"It's very un-Jedi-like of me, but I want to break his record."
He learns it after one day and four hours of study.
Harry Potter is an instant expert at flying the first time he rides a broom the first book, because it wasn't the first time. He'd been given a toy broomstick on his first birthday..
In High Wizardry, the third book of the Young Wizards series, Dairine has the entirety of magical knowledge downloaded into her mind, which, combined with the massive amount of raw power she has, allows her to single-handedly fight the Lone Power to a standstill. Then the Big Bad pulls an And Your Little Dog Too, giving her the motivation to instantly devise a massively complex spell which actually defeats the Big Bad.
When the refugees from a high-tech society end up living off the land in Orson Scott Card's Homecoming series, they need to relearn things like making/using bows and arrows. So they go to their computer god and ask. Unfortunately, transferring thoughts from one mind to another is painfully impossible, so they end up receiving muscle memory instead, as that's just reflex rather than conscious thought.
Second-stage (and above) Lensman in E. E. “Doc” Smith's stories are capable of extracting huge chunks of knowledge and skill from others' minds with some rapidity, and also of granting such to others (eg. 'teaching' someone used to 1940's tech everything about the operation of blaster pistols and spy rays near-instantaneously).
Doctors in James White's Sector General stories can, if of sufficient mental health, have the entire medical knowledge of a master-surgeon of an alien species temporarily downloaded into their heads, to allow them to operate on that species without having to spend years learning their anatomy. With the downside that the donor being's personal quirks, racial traits, nightmares, sexual fantasies, and concepts of what makes a good lunch are also stuffed in there...
Of every accomplishment accustomary to my sex, I was Mistress. When in the Convent, my progress had always exceeded my instructions, my Acquirements had been wonderfull for my age, and I had shortly surpassed my Masters.
Zoey Redbird of The House of Night has super-special Elemental Powers that she doesn't even need to practice to use without breaking a sweat. All she needs to do is to wait until her goddess-given sixth sense tells her exactly what she needs to do, and she can turn invisible, fly over walls, blow opponents off their feet, hurl fireballs, regain the memories the Big Bad wiped from her mind, restore the humanity of bloodthirsty vampyres, and much more without any beforehand practice whatsoever.
Charlie (and Sylar through power theft) can not only remember everything she read but could also properly apply it as well.
In Season 2 there's also Monica who is able to instantly learn how to do any physical skill or martial arts maneuver she's physically capable of simply by watching anyone else do it once, either live or via recorded media.
Sylar's main power is the ability to "understand how things work," which goes towards explaining how he's able to rapidly master all his stolen abilities. And even he has to take a few days to iron out the kinks in particularly cumbersome abilities, such as superhearing (high pitched noises become a Weaksauce Weakness) or shapeshifting (involuntary shapeshifting due to major psychological issues).
Initially subveted with power sponge Peter Petreli, who has to be near someone to use their power and has no control over the power, as shown when he meets Claude and automatically becomes invisible. After some training he is able to control them, but when he gets too many he has trouble suppressing all of them and goes of like a nuke. After that though he never has any issues again and can immediately use any power he gains.
Ted Sprauge has no control over his nuclear based powers for most of the first season and constantly emits radiation (which kills his wife via cancer) or explodes when under stress. While Sylar is instantly able to control his power near perfectly, Peter is not so skilled and nearly blows up New York
The 1980s show The Greatest American Hero is a funny aversion to this trope. The main character receives a super-powered suit as a gift from aliens, but unfortunately lost the manual. So he has no idea what powers he has, or how to use them.
Lana Lang in Smallville learned kung fu in three days. She also learned how to successfully run her own coffee shop instantly and while still in high school. The big issue with her was that she kept knowing how to do things someone in her situation would not know in order to keep her plot-relevant. The coffee shop was to explain why she kept getting involved in things-the whole school hung out there, Clark included. The kung-fu and so called "military training" were becuase the writers had finally listened to all the Distressed Damsel complaints about her character. The second she needed to know something, it was known so they could say she was still relevant (when she was well past that very quickly).
In "Leech," Jonathan points out to Clark (who has recently been Brought Down to Normal) that it took him 12 years to learn how to use his powers properly. In the same episode, the guy who gained Clark's powers masters them in the space of about a day.
Subverted in Firefly. Malcolm has to learn to duel with swords overnight. In the actual duel, he seems to be doing well at first, but his opponent is only playing with him. He does win the duel, but with combat pragmatism rather than fencing skill.
River is implied to be one of these. Aside from being a gifted savant, she also possesses literal mind-reading powers, enabling her to pull complex knowledge from other people's minds, and it is implied that she had this ability even before she ended up in the Academy.
Xander kept his military knowledge for a couple of years after the Halloween incident where everyone became their costume. By season 4, two years after the initial incident, his soldier memories were pretty much gone.
One of the powers of the Slayer is knowing how to use a weapon just by picking it. They still have to train to master it, though.
Averted in "Earshot". Buffy gains telepathy by coming in contact with a demon, and suffers Power Incontinence. She doesn't just overcome it and learn to control it; instead, she's unable to stop it at all and suffers intense mental trauma from hearing dozens and dozens of thoughts all going on at once. She only gets better when her friends manage to cure the condition completely, meaning that she never learns how to control her newfound, shortly-lived telepathy power.
The ability of imprinting technology to make Actives experts in any given field at the press of a button is a series premise of Dollhouse. However, it's not possible for a Doll to possess more than one set of skills at a time without being wiped and reloaded... until Echo starts retaining imprints and they load her with every combat-based imprint they have.
Also something of a subversion, as the imprints are based on the personalities of "real" people who wereTaught by Experience. Mixing and matching individual personalities to create a coherent imprint for each engagement is likewise a far from instantaneous process.
This trope is pretty much what makes the title character of Kyle XY so special.
The whole shtick of The Pretender: with a little learning time, Pretenders such as Jarod could master any role from janitor to astronaut.
A standard of the Power Rangers series, where the characters generally are barely old enough to have a driver's license, yet can handle a giant robot without so much as a training montage.
The very first episode has Trini and Billy lampshade the fact they can pilot the Dinozords. It seems their powers provide the knowledge as well as fighting skills. Played with in that the heroes don't retain these skills when they change back: Billy still has to train with Jason and Zack to build his martial arts skills.
Averted with Ziggy the Green Ranger in Power Rangers RPM (it only took them 17 seasons) who doesn't get an instant martial arts download into his brain, and the other rangers were hand picked martial artists. Though he can pilot his Zord better than he can a car, he still needs to get to grips with it.
Also averted in Power Rangers Lost Galaxy. Waving your arms and yelling "Galactabeasts, over here!!" is not how you summon the Megazord
Also, a bit of a subversion for Power Rangers Time Force since their in-helmet visors show them what to do when operating their megazords for the first time as well as some new weapons. Eric even has a nice AI to instruct him on his new tech. And since the others were time force operatives and Eric was a trained fighter, the rest probably came naturally. Wes, on the other hand, had some difficulty at first, though he got the hang of it.
In Power Rangers Lightspeed Rescue, the heads-up display also tells them of their new tech and Mission Control tells them how to operate things as well. It was the first series to have tech-tech instead of Magitek and so such things were often turned on their heads.
The title character of John Doe is a perfect example of this - he can look up any piece of information at any time, making him an expert in every field. This is consistently shown as he flies a helicopter with no training, is a capable doctor, makes significant profits in the stock market, and pulls off MacGyver-esque stunts.
Not content at being the World's Greatest Diagnostic Physician, an accomplished musician and speaker of several languages, House recently was advised to get a hobby to help manage his pain without Vicodin. He accompanies Wilson to his cooking class, and by the end of the episode is told he has created "the best thing I have ever eaten."
Between seasons nine and ten of CSI: Crime Scene Investigation, Ray Langston went to CSI school in a big way, and instantly caught up to (and possibly surpassed) the regular crew on suspiciously specific scientific knowledge.
It's Always Sunny in Philadelphia: Resident ding-bat Charlie apparently learns to play the keyboard with almost no practice, saying, "Keyboards just make sense to me."
As the carrier of the latest version of the Intersect, Chuck can do about anything that a World Class Spy can do, and then some.
It's never drawn attention to but Dharma from Dharma and Greg is repeatedly shown to master complex skills in a matter of hours. All of them are forgotten by the end of the episode.
In Stargate Atlantis, season 5, "The Prodigal," Michael and his hybrids are immediately able to use the Atlantis computer systems with ability similar to experts like McKay or Zelenka. When Michael was on Atlantis, he was never given the opportunity to learn how to use their computers, nor were any of his hybrids exposed to Atlantis' computers. It is not credible that they would be able to use the Atlantis computers to lock everyone out or to set a destruct, or even use them at all without some prior training in human and Atlantean computers.
In Stargate SG-1, "Prometheus Unbound" the enemy character, Vala Mal Doran, not only is able to take over the ship, which is not possible the way she did it, but she instantly knows how to use the Prometheus' computers and is able to lock Jackson out and to run the ship. This is not possible, as it's the enemy's first exposure to human technology. She wouldn't even be able to read English using the Latin alphabet, never having been exposed to it before. But she can run the computers like Steve Jobs?
At least it's given a Hand Wave: she learns VERY quickly, presumably as a result of latent knowledge from being a Goa'uld host (though how that would help with using Earth-based technology is anyone's guess.) Also, it isn't immediate; she does have to spend time figuring out the computer system, which is why she kept Daniel on the ship in the first place.
Star Trek: Enterprise, "In a Mirror Darkly", has four individuals who become instant experts on running a Starfleet vessel, the U.S.S. Defiant, 100 years more advanced than they are used to. They are able to get it up and running and into combat within ten minutes. This would be like naval officers in 1912 trying to run a 2012 nuclear-powered aircraft carrier. They might be able to navigate the carrier, but they would have no clue of what most of the systems on the carrier would be. Fission didn't exist back in 1912, nor did the electronics, nor did the weapons systems. It would take a week just to crack open the manuals and find out what the major systems did. Starting up the reactors and running them would be impossible without a knowlegeable crew. Learning the basics of arming and firing the weapons would take days. Ironically, Archer and company could easily do it if the timeline was anything like the original one that Roddenberry wanted (the 1980 book Star Trek Spaceflight Chronology is based on that timeline) as the technology of the Defiant would about roughly 20 years more advanced than what they were used to. The Baton Rouge Class of the STSC of 20 or so years before the Constitution Class is roughly the equivalent of the NX Enterprise (except it had shields but no phasers) but it would not be that much of a stretch for a Baton Rouge crew to start up and operate a Constitution Class like the U.S.S. Defiant in the manner shown in those few minutes
Played for laughs (and to give Bill Bailey a chance to show off) in an episode of Black Books. Manny sits down at a piano, idly taps a couple of notes, then instantly joins in with the music playing on the radio, much to his own surprise.
Mycroft pretends he learned serbian in two hours in Sherlock.
GURPS has the advantage Wild Talent which is an odd version of this trope. A few times per game you can try absolutely any skill at better than default (a Medieval ascetic can try to program a superscience computer from ten thousand years in the future). For a few points extra this event provides enough experience to gain a level of skill.
Mind Mages from Mage: The Awakening are the kings of this trope (especially the powerful Mind mages, apprentices still exhibit this trope but to a lesser extent). They can, at any time, instantaneously learn any human skill, talent or knowledge. A Mind mage can become the master of kung fu, a virtuoso, a genius computer hacker or compete with a Nobel prize winner in his own field within seconds. Coupled with their ability to instantaneously alter their innate intellectual and social capabilities(becoming more intelligent, more charismatic etc.) and there's virtually no non-athletic human achievement they can't duplicate(and even if they can't be the absolute and utter pinnacle of physical achievement, often they can still be scarily good). If they combine that with Life magic - which allows for the raising of physical attributes - then there's virtually no mundane feat that they can't duplicate. This is a slightly contentiousissue.
Time Mages do them one better by temporarily rewriting their history so that they not only always knew how to operate widgets at a world-class level, but they grew up suited to the task (base stats changed to optimum) and have all the associated credentials, i.e. a Ph.D in widget operations and three Nobel prizes in widgetology, granting them access to and knowledge of all of the resources that a world-class widgeteer would normally possess. For the extra cheap-shot, life and mind can add more stats on top of this as above.
It can even be argued that this is the core theme of Mage in general. The name of their casting stat is gnosis, which is an old word for divinely granted knowledge (as opposed to learned or a priori knowledge), aka the medieval word for this trope. Their magic isn't power so much as instant understanding of how things really work and where to nudge for maximum effect.
First-level abilities generally reflect this: Matter - instantly understand how to operate a machine, Mind - instantly know how to interpret expressions, Fate - instantly understand how things fit together, Death - instantly understand how things decay and wear down. Etc.
In Exalted, training in favoured or caste abilities takes no time. Spend the XP, and presto - instant competence.
Many Exalted (especially Solars) can also learn Charms that allow them to instruct others in record time.
One notorious goof in the first edition Autochthonian book's widely hated Locust War chapter had the Autochthonian invasion force become masters of ship-to-ship combat who neatly pwned the Realm Navy, despite it being only a few months since the first time they saw an ocean.
Since its creation, Dungeons & Dragons has allowed characters to instantly gain new skills, languages and even entire classes at level up.
Pathfinder has a clearer example. A character who raises their intelligence may gain new skills. Pathfinder, unlike some editions of Dungeons & Dragons, makes all bonuses for high scores retroactive, including skill points gained for a high intelligence. This means if a very powerful character raises their intelligence and gains skill points, they could dump them all into one skill and become one of the best in the world instantly.
In Changeling: The Lost, the titular changelings can use pledges to raise some types of skills or gain new ones at will, albeit temporarily. They can even use pledges to give other people those skills, and if the other person is a normal human, they can achieve even greater levels of expertise, up to a rating of five on a five point scale; supernaturals can only gain ratings up to three.
Members of VASCU in Hunter: The Vigil have a high-level power that enables them to temporarily become expert in a skill (or competent at a group of skills).
An explicit power of Tech Specialists in the Star Wars d20 RPG; the Instant Mastery class feature gives them proficiency in a new skill at certain levels, raising any skill they previously didn't have to 4th rank (the maximum a level 1 character can have).
In Aberrant, Mega-Intelligent Novas can take the "Mental Prodigy" enhancement, which makes them an instant expert in a particular intellectual field (be it science, engineering, medicine, investigation, finance, or something else), usually better at it than those who have trained in it all their lives. The sourcebook Brainwaves, which was only released unofficially after the line had already been cancelled, would have added the "Fast Learner" enhancement, which would have allowed the Mega-Intelligent to learn new skills faster (i.e., with less Experience Point expenditure) than other people.
In Deus Ex, the player is allowed to train JC's various skills by using skill points gained at various points in the game. However, all that is needed to gain/upgrade a skill is the appropriate amount of skill points, and they can be learned at any time with immediate effect.
Celes from Final Fantasy VI is somehow able to not only pick up the ability to learn opera, but is also able to memorize an entire musical score in the space of an afternoon. She does it well enough to be a convincing facsimile of the famous opera singer she resembles, to boot. But damned if singing her Leitmotif isn't nifty.
She does only end up singing in Act I, before an unexpected interruption or two; and it would seem that she only had one big aria, a small piece of recitative and a couple dances. There's no reason that, coming from a cultured Empire, she couldn't have learned to act, sing, and dance in her upbringing - Kefka has some serious vocal projection abilities and a flair for the theatrical, and Gestahl proves a capable actor (or at least liar). And we have no real idea how popular that particular opera is; it may be all the rage in the Empire these days, so she might have prior knowledge of all the music. All that being said, of course, the woman is a general, not some opera floozy.
Dante from Devil May Cry seems to be able to use a new type of weapon just by picking it up, as well as gaining new moves just by paying for them. The move-acquisition is handwaved by the existence of the Time God, who grants "the power of the ancient magic clans."
Vergil can do it too, so it's hand waved as just being something that Sparda's family is capable of doing. Nero, on the other hand, never gains different weapons from those he starts with- he simply gains new techniques.
Also note that, except for the weapons they start out with (and presumably have trained with for years), all of their Devil Arms are living weapons that have acknowledged them as their master. The weapons themselves could be contributing to their skills.
Link displays this to the degree that fans argue that it might be a side-effect of the Triforce of Courage. No matter how odd a new item is, he instantly acquires the knowledge how to use them when he picks them up, despite the fact that he usually starts the games living a fairly normal life. It's more believable in The Legend of Zelda: Twilight Princess, where he had Epona for a while and had a mentor teaching him a thing or two. Then again, the game also had some of the weirdest items in the series such as the Spinner (an apparently magical cog that can be used to ride on rails).
However, it is questionable if this is because of the Triforce: In The Legend of Zelda: The Wind Waker, where he starts out without the Triforce of Courage (he gets it near the end of the game), Orca gives him his very first sword-lesson ever, because he reached the age of twelve - and comments on how amazingly good he already is for a beginner.
In The Legend of Zelda: Majora's Mask he demonstrates that he can also master new bodies. For instance, after getting a Goron body, he succeeds where the Goron hero failed, rescues all the Gorons, wins their races, and gets himself nominated as their new leader.
It's implied that knowledge and memories come with the transformation (and some are lost when back in normal form): Link can never read Goron or Zoran text as a human; he has to be transformed into the relative form to do so.
In many MMORPGs, learning a new spell or ability is usually just a matter of shelling out the appropriate amount of cash. World of Warcraft averts it with weapon skills, which need to be trained to be effective (although any effect from equipping a weapon other than being able to whack things with it are instantly available when you learn the skill. Depending on the item, this can vary from improving spells to being able to open a portal to a specific location).
Played straight after multiple patches. Weapon skills have been removed, allowing players to freely use any weapon they have the ability to equip, and skills are now automatically learned on leveling up rather than at trainers.
There is a Hand Wave in City of Heroes, in that you gain immediate benefits from leveling (increased HP), but in order to get new skills, you have to visit a trainer.
In Knights of the Old Republic, the main character picks up Jedi proficiency with a lightsaber and Force powers in a matter of weeks, where most Jedi apprentices take years. In this case the main character actually was a Jedi for years, then had his memories wiped as part of a brainwashing program. So the training really only had to reconnect the main character with their former powers.
Knights of the Old Republic II actually makes this a plot point. You spend much of the game seeking out Jedi masters who teach you new force forms or lightsabers techniques, afterwards remarking in amazement that you're able to learn highly advanced techniques that should take you years to perfect in a matter of minutes. If you choose to attack the Jedi you find instead of gathering them, you go one better and can actually learn their techniques by watching their technique as you're in the process of killing them, which horrifies them.
Half-Life: Gordon Freeman, a theoretical physicist from MIT, came to work one day, and the place swarmed with aliens. Ever since he picked up a crowbar, he started kicking unfathomable amounts of ass, including use of every weapon he ever finds without even the slightest hint of natural inaccuracy. This is the guy who can hold and use a rocket launcher with both hands while climbing a ladder.
This is even lampshaded in one of Dr. Breen's broadcasts in Half-Life 2, chewing out the Combine Overwatch for their inability to capture or kill Gordon despite his lack of weapons or tactical training.
While still qualifying as this trope, it isn't as ridiculous as it sounds, as the optional training level for the first Half-Life has Gordon receiving firearms training in a hazard course, so he at least has some experience with them. It's when he proficiently uses things he's never even seen before (like the nuclear cannon or the alien weapon that fires hornets) that it becomes silly. It also makes Adrian Shephard from the Opposing Force expansion an example of this trope, as not even career soldiers receive training on operating a symbiotic insect that fires electricity or a larval alien used to launch spores.
Vagrant Story gives us Ashley Riot. Physically, he's an unstoppable powerhouse who gradually "remembers" techniques he once knew, and can use every weapon he finds. With the proper equipment, he can smith his own armor and weapons, even though some of the metals are explicitly described as not being found outside of Lea Monde. But the real kicker is that he can learn magic just by reading a tome. And after killing a Lich, Ashley learns to teleport by its spirit speaking to him. There is some implication that The Dark is awakening latent talents within Ashley, but that doesn't change the fact that Agent Riot has a steep learning curve.
In Prototype, Alex Mercer gains the knowledge of those he devours, giving him an easy two step process to becoming an instant expert: 1) find an expert who's spent the requisite years and years of training and practice, and 2) eat him. He uses it to learn how to use firearms, operate helicopters, and lots of other stuff a biologist wouldn't otherwise be able to do so well, and that a virus couldn't usually do at all.
In Star Wars: Dark Forces II: Jedi Knight, the protagonist (who had previously just been a first-person shooter hero for a game and three levels) is instantly and completely proficient with a lightsaber, having the exact skill level as he does at the end of the game, arguably better than all seven bosses at dueling. Then he goes on to gain powers at the Jedi Master (later "Jedi Lord") skill level after a few days or weeks at the most.
In Real Life, changing from one aircraft type to another requires at least some cross-training. In Ace Combat, Air Force Delta, Tom Clancy's HAWX and other flight sim-shooters, the player characters can jump between aircraft from any country in the world and have no problem controlling it flying it to its maximum capability and leaving a trail of smoking aircraft wreckage. Of course, this is partly excusable by Rule of Fun; Anyone remember flying school from Grand Theft AutoSan Andreas?
Done unusually in Morrowind and Oblivion. You can equip probably any type of weapon as soon as you find it, but you only become stronger with weapons and skills (including specific types of magic, such as destruction or restoration) that you actually use. The part about being able to outclass ancient NPCs still applies, though.
In Fallout 3, you can go from being a totally useless unskilled vault-dwelling teenager who has had some practice with a BB gun as a child, to being a complete badass after only a few weeks in the wasteland, mastering a range of extremely difficult skills and professions, such as:
Picking complicated locks and hacking military grade computer software like a professional security expert.
Performing complicated surgical procedures that should take years to learn for a medical degree.
Becoming an expert in negotiation, to the point where you can persuade almost anyone to do anything, and be such a master salesman that you can convince people to buy sand in the desert.
Learning to be as stealthy as an actual ninja, hiding in plain sight where you should easily be seen and being able to kill people in one blow with your bare hands if necessary.
Most importantly, being able to not only proficiently use any firearm you encounter, from a simple hunting rifle to a plasma gun, laser minigun, gauss rifle, or almosr any weapon you can imagine, but you also intimately understand how they work and how to cannibalize other weapons to keep them working in absolute perfect order.
Atleast the game explains it with the perks you take. Daddy's Boy/Girl let's you gain a certain amount of Skill Points into Medicine and Science, since your dad was a doctor in the vault. Some of course the way that the player character can equip any weapon and use it differs how ever. Than again the Pip-Boy tells you the name/type of the weapon, so you guess that how you know how to work it.
Averted in the second Master of Orion game, where only telepathic races can immediately use captured ships.
This is actually part of the plot in Assassin's Creed II: the main character (Desmond Miles) is put in a machine called the Animus to relive the genetic memories of his assassin ancestor, Ezio, in the hopes that he'll gain Ezio's skills in a few days rather than years. Still used straight with Ezio himself, though: The various kinds of weapon-fighting might have been taught to him in the past, and the training under Paola and Mario is given the flavour of a Training Montage - made explicit in semi-novelisation Renaissance - but he takes to the Hidden Blade incredibly fast with no apparent reason for it.
Super Mario Bros. (and its spinoffs). Mario doesn't apparently even need to train to suddenly learn new abilities once per game, master new power ups and items per game, and be good at every single sport he's tried in some way. In the RPG games like Paper Mario and Mario & Luigi, he can literally get a new item or ability one minute and have apparently completed mastered it the next.
Double subverted with the Bros. Attacks in Superstar Saga in that the powered up Advanced versions can only be learned after using the original a bunch of times (and a cutscene when they are unlocked where Mario thinks of the technique), but both the original and the Advanced are instantly mastered (provided you know the button combos) upon unlocking them.
Kirby. Despite just having copied a creature's ability, he's able to use it instantly without problems (unless certain abilities are problems themselves...I'm looking at you, Sleep Kirby). Plus, at least by animecanon, Kirby is only an infant (which isn't farfetched, seeing him in-game).
In Company of Heroes, even though a battle hardened American Riflesquad can crew a German Pak-38 and know exactly how to use it, any combat experience they have as Riflemen is lost, and must be regained as an AT Crew.
Furthermore, is the American Veterancy System. For example, a Riflesquad takes about 18 kills to gain Vet 3 (the highest). A Vet 3 Riflesquad can outfight an Elite Stormtrooper squad fairly easily. So that's 3 kills per person, and suddenly they're more skilled than Germany's best. Even more so as veterancy is not diluted by replacements, so five green-as-grass recruits can outshoot those stormtroopers as long as they have a veteran to give them some pointers on the way back to the front line.
In all of the Grand Theft Auto games the protagonist can learn how to use any weapon or vehicle from the moment they see it. The most ridiculous example is CJ from San Andreas, who can load and fire any weapon from an M1911 to an SA-7 Grail rocket missile launcher simply by picking it up, and goes through a few (videotaped) lessons to learn to fly any aircraft. The height of ridiculousness is "Vertical Bird", where he sneaks aboard an amphibious assault ship, eliminates about a dozen trained soldiers with either stealth or firepower, and hijacks a Harrier jumpjet to shoot down two other fighters and destroy several boats. Quite impressive for a two-bit gang member from the ghetto.
Travis Touchdown from No More Heroes, who won a beam katana in an online auction and entered the assassination scene and entering the country's top 11 seemingly with no training in between.
Although he didn't train with the beam sword, his conversations with shinobu reveal that he did have some training with swords... via mail order instructional videos produced by shinobu's father, so that's not much better.
One of the manuals has stated that he took classes from a correspondence class for the sword techniques, and trained in Calgary for the wrestling techniques, along with his mentor Thunder Ryu.
Stocke from Radiant Historia, although it can be handwaved as him literally having all the time in the world to practice. Having a time travel mechanic at his disposal means his skill acquisition could only look instant to an outside observer.
The nature of fadeouts during the learning scenes and comments from his teachers directly imply this is the case. In the one instance Stocke inarguably learns a skill on the spot with no chance to repeat it, said skill is a property of the artifact he's been using the entire plot, copied from the weilder of said artifact's twin.
In The Elder Scrolls V: Skyrim, anyone willing to devote themselves to a lifetime of training can learn to use the reality warping language of the Dragons, the Thu'um. But only a Dragonborn like the protagonist can master Dragon Shouts instantly after reading the words and absorbing dragon souls. This is because the Dragonborn is a mortal with the soul of a Dragon.
Pointedly averted in Homeworld: Cataclysm. Whenever a new technology is researched, it's not applied instantly to all units but small craft have to be recalled into a hangar for refit and capital ships have to go offline for a short while as the crew installs the new equipment.
It gets even better with the Beast who can only aquire some technologies by capturing an enemy ship in possession of said tech; once the unit is captured, it must be brought into a hangar and disassembled before the tech is even available for research. What makes it an aversion? The Beast is a technoorganicsubversionentity that otherwise plays this trope straight by growing upgrades in the field and presumably sharing instructions among their selves.
Dynasty Warriors: Online has each weapon contain the move-set of a character. The trope comes into play that one can copy that weapon's moveset from the original holder the moment they touch it, so they could go from welding a spike ball as big as them to knock enemies 50 feet in the air to using a fan with such grace they glide through enemies. While they do have practice it's very optional, but it is fun to do so you might not avoid it all together. The only real change his first charge attack in the combo and the 6th, but those vary from individual weapon to individual weapon, so two flutes might have a slightly different combo.
Both played straight and averted in Battlestar Galactica Online. On the one hand, once you pass a certain level you can immediately upgrade to a new starship type without having to go for special training. You also don't need special training to switch between ship models. On the other, the skills that you can train ingame to improve your performance take a clear amount of time to complete, which gets increasingly long as you go up.
Atlantis The Lost Tales: Seth learns to fly a flyer with great skill immediately after gaining the ability to do so.
The single-player campaign in Operation Flashpoint averts this by having you shift between four different playable characters who each have missions falling within their own specialization: an army corporal does frontline fighting, an air force pilot and a tank commander do the obvious, and a special forces operative handles scouting and sabotage behind enemy lines.
Played straight in this strip, where Vaarsuvius casts a single spell on Belkar (the callous, bloodthirsty halfling) that unlocks his potential as a healer and enlightens him to a life of kindness. Luckily for the fans, the spell doesn't last.
In that case, though, the trope if not the attitude adjustment is justified; these are skills he should and technically does have, but he can't use them because he's using a suboptimal build for his class (like, way below par; even with his race and size bonuses, he's out-stealthed by Haley, a vanilla human rogue). V's spell gives him the capacity to do what he'd be able to do anyway if he had any interest at all in actually being good at his job.
Lampshaded in this strip when Elan figures that he can instantly gain decades of arcane knowledge by dual classing to Wizard; Vaarsuvius, who spent a century studying arduously for this knowledge, is not amused.
In Homestuck, going God Tier gives you an instant mastery of your powers as well as instant knowledge of everything you're capable of.
Despite all this, she still needs to keep working on basics — so in a sense, she has to learn backwards.
Played straight with annoying regularity in Survival of the Fittest. Many characters pick up their weapons and seem to immediately know everything about it, despite there being absolutely no (or only a tenuous) reason for their knowledge. Although instructions are provided this still does not fully justify this trope's presence. On the other hand, there are, admittedly, some characters who would have the knowhow due to prior experiences.
Invoked and parodied in Immersion when they decided to test how well two shapely martial artists would cope fighting in video game costumes. They erred on the side of shapely since it is quicker to learn martial arts than to improve your looks.
Sokka also inexplicably learns to use the sword in a matter of a days. Not even Training from Hell would be able to give normal people any passable sword skills in that manner of time — and Sokka seems to spend just as much time doing calligraphy and feng shui as actual sword practice during said days.
In the interest of fairness, they had been training their skills casually since before they met Aang. Sokka was already proficient with his boomerang, club, spear (though it got broken right away), and machete at the start of the show.
It makes more sense that what Sokka picks up from Piandao is not so much proficient swordsmanship as it is adaptability when using a sword, even if you're not very good, because it's that which can make the difference. Something which as a non-bender Sokka was already aware of; he's at a clear disadvantage but survives because he's figured out how to get by when others rely on bending.
Aang, much to Katara's jealousy, masters moves from a waterbending scroll she picked up. Justified in that it's Leaked Experience from all his previous lives as Avatar with Roku saying to one of his teachers that it's more like remembering a distant memory. It should aslo be noted that Aang picked it up faster because Katara was teaching him what she had to learn by experimentation, something Aang himself notes.
Averted by Korra in The Legend of Korra. While she can bend multiple elements years long before she's supposed to be able to, it still takes her fourteen years of intense training to master three of them. That amounts to a little over four and a half years per element. Once the series starts and she begins her airbending training, her progress is slow due to Air not being suited to her non-spiritual personality and confrontational attitude.
Averted once again with Asami and mecha-tanks, but played completely straight with General Iroh and airplanes.
Toyed with in Megas XLR. The main character, Coop, is (usually) an expert at piloting his enormous mecha, Megas. However, this is only because he had specifically modified it to control just like the video games he'd been playing his whole life. When Kiva (an experienced pilot who was designated to pilot Megas before Coop modified it) attempted to pilot it, she could barely get it to go in the right direction.
In the Chip 'n Dale Rescue Rangers episode "Prehysterical Pet", an alien dinosaur learns English in just a few hours by reading Dale's comic books.
Starfire of Teen Titans can learn languages instantly just by kissing the speaker on the lips.
That's straight from the comics. Like in the show, she does this with Robin when she first arrives on Earth.
Lexington of Gargoyles, despite having only lived in the twentieth century for a matter of weeks, manages to build a motorcycle from spare parts and restore a crashed helicopter to functioning condition. He also pilots said helicopter, having practiced his skills by fiddling with a helicopter flight simulator game given to the clan by Elisa.
Frequently averted on Jackie Chan Adventures, which features a set of talismans that grant any of a variety of magical powers. Even the good guys don't always use them to their full potential (though of course they do so most often), especially if someone gets them to drop their talisman.
Occasionally subverted for comic relief. An excellent example is the super-speed talisman, which has been defeated at least twice by dodging to the side, leaving the overconfident user to smash face-first into a wall.
The Highdefdigest review for Iron Man: Armored Adventures likes how in the first episode Tony's still (realistically) getting the hang of the suit, but gripes about how by the second episode he's already an (almost-)Instant Expert at it: "It's unfortunate he's already a pro by the second episode, but it's still nice to have some bit of believability, if even brief."
Used in Futurama when Bender temporarily becomes captain of the Planet Express, much to Fry's annoyance. When Fry lambastes him and accuses him of not knowing the first thing about being a captain, Bender instantly reads the entire manual and then uses the info to chastise Fry.
Fry: Have you even read the captain's handbook?
Bender: (flips through entire manual) I have now. And what's Peter Parrot's first rule of captaining?
Fry: (defeated) Always respect the chain-o-command...captain.
There's also Twilight Sparkle. While attempts to learn spells tend to be hit or miss, she's been shown to perfectly duplicate anything she's witnessed directly. Examples include being able to teleport properly after seeing Nightmare Moon do it once, and learning dark magic simply from watching Celestia do so during a presentation. In the latter instance, at least, it took considerably more effort on her part than the princess needed.
There is a concept called "The Natural Athlete," where the knowledge, skill, and physical ability of an individual allows them to succeed at nearly any sport whether or not they have spent time training for the needs of the game. Just having a natural gift for hand-eye coordination is invaluable in shooting a basketball, being a fast runner with quick feet is useful in football, etc.