My Skull Runneth Over

"The wizard who reads a thousand books is powerful. The wizard who memorizes a thousand books is insane."

- flavor text on the Magic the Gathering card "Battle of Wits"

So you're walking along, minding your own business, playing with your iPod in a neutron storm next to a nuclear plant during the equinox, and suddenly some Applied Phlebotinum grants you a magnificent gift: an entire library's worth of information is downloaded directly into your head, along with all the intellect, memories and wisdom needed to use it. You become an instant genius at everything from knitting to astrophysics, and you can suddenly Techno Babble your way out of any problem!

Except... for this problem:

The thing about super-human knowledge and intellect, is that often you don't get a super-human brain to put it in, and there's only so much room in there. As your brainpower goes up, your survival rate goes down. Time is running out, and you either have to figure out a way to ditch your new super-smarts or die - either by hemorrhage, cranial explosion, or body strain.

Occasionally dying isn't the problem: It might be non-fatal, but have some other significant drawback if you don't get rid of it soon, such as madness, head-splitting migraines, overwriting of memories or knowledge, or permanent brain damage.

Compare Deadly Upgrade. Also compare The Fog of Ages, where an immortal being has been collecting memories for so long that they're overwriting the oldest ones. Not to be confused with My Brain Is Big, where the skull literally runneth over and the brain shows outside it. See also Super Intelligence.

Anime & Manga

 * In Osamu Tezuka's Phoenix story "Civil War", the historical figure Taira no Kiyomori desires the blood of the titular bird so he can become immortal and continue to lead the Taira Clan, instead of letting it get run into the ground by his incompetent sons. He starts having second thoughts, however when he has a vision of himself in the 21st century, where he's become an invalid due to his brain having run out of space for new memories and has to be periodically hooked up to an "Amnesia Machine" or he'll go crazy. Other characters who do gain immortality, or at least very long lifespans don't seem to have this problem, but that might just be because they usually end up becoming hermits whose lives are largely monotonous.
 * This is pretty much the plot of the first arc of To Aru Majutsu no Index. The titular character, Index Librorum Prohibitorum, is being used by the church as a library of every magic tome in the world, using her eidetic memory. However, because it uses up most of her brain, they periodically wipe her other memories (ie: her memories of her own life).
 * In Ghost Sweeper Mikami, Dr. Chaos's brain really is completely full with information. So what happens when he learns something new? Rather than expand and strain itself, his brain simply overwrites the earliest thing it can. So while he is an occult genius who can readily comprehend many mystic things, he can easily forget such basic things as what 2+2 results in (hint: not 5).
 * Played for laughs in K-On!, where Cloudcuckoolander Yui forgets all the chords she learned after cramming for an exam.
 * This is how Ed describes the feeling of going past the Door of Truth that connects humans with the ability to use alchemy in Fullmetal Alchemist.
 * Except that in his case, he wants to do it AGAIN.
 * Well, no one said he was rational at that time.
 * The titular character of Naruto faces this downside to his Shadow Clone training strategy. With hundreds of clones he can experience years of training in one day, but the backlash when the clones disperse is enough to render him unconscious while his brain tries to process the information.
 * At the end of Divergence Eve.

Card Games

 * Several cards in Magic the Gathering provide extra draws (and thus, potentially knowledge of additional spells in-game) at the expense of life points, making overuse of them naturally dangerous. And not all of them can be easily "turned off" once in play...
 * The other danger of excessive card drawing is that you lose the game if you have to draw from an empty deck. There are several tournament strategies that involve generating obscene amounts of mana, then dropping a Stroke of Genius or similar card to make an opponent draw their entire deck plus one card.
 * Also, the hand size limit may be a less lethal example of the trope. A player can technically end up with any number of cards in his or her hand for a time... but at the end of his or her turn, he or she has to discard any in excess of his or her current maximum hand size (which usually starts at seven and stays there unless modified by specific effects), presumably reflecting how much arcane knowledge his notional brain can safely hold for long.
 * The card Rush of Knowledge mentions this; "Limitless power is glorious until you gain limitless understanding", the picture shows a mage receiving knowledge, much to his discomfort.

Comics

 * In an issue of The Sandman, "Calliope", Dream punishes an author by giving him an overload of ideas, so much so that he starts writing them on the walls with his bloody fingers.
 * This was a plot of a Nightmare Fuel horror comic from the Silver Age. The man gets hit with a evolution-devolution ray, and as his head starts to evolve and gets bigger (in the traditional Future Human way of comics from the time), his body "devolves" to that of a tiny lizard.
 * In PS 238, a scientist managed to both figure out time travel and learn all of the world's knowledge up to the late 90s by uploading an encyclopedia into his brain. It made him so crazy that he used his time travel abilities to be both a superhero and his own nemesis.
 * In the Captain Atom / Wildstorm crossover, Cap does this to Voodoo when she tried to invade his mind. He uses his neural uplink to the Pentagon's computer net to basically KO her with the Internet.
 * In his first appearance, The Leader - superintelligent enemy of the Incredible Hulk - was after an Ultimate Machine containing all the knowledge in the Universe. When he obtained it and downloaded the information in his mind, this proved too much even for his super brain and killed him. Seemingly.
 * In an issue of Dylan Dog, a scientist is looking for a way to unlock the full potential of the human intellect, but all of his test subjects die in predictably gruesome ways. It turns out that an adult's intellect is "atrophied" after a life of underuse, and only babies are flexible enough to survive the process. When the scientist, mentally unbalanced after years of frustrations, experiments on his newborn daughter, it finally works even too well.

Film

 * At the end of Indiana Jones and The Kingdom of The Crystal Skull,
 * The film version of Johnny Mnemonic, with the additional kick that the protagonist doesn't actually have access to the downloaded knowledge that's killing him -- he's a courier hired to carry data securely in his own "wetware".
 * The Computer Wore Tennis Shoes (1995 version). It was not going to destroy him in this case, but got erased with a "magical noise virus over the phone".
 * Subverted in Flash Gordon, in that Zarkov's brain was to be erased and reprogrammed, but Klytus ordered it to be done "only to Level 3", as he doubted Zarkov's Earth brain could take any higher level. After he leaves his assistant orders him programmed to Level 6. Further subverted in that.
 * suffers this fate near the end of Forbidden Planet, after intentionally overusing a Krell learning machine to try to figure out what's killing them.
 * In Phenomenon, George Malley has a UFO encounter that gives him advanced brain processing power and telekinesis. However, it also gives him a brain tumor.
 * Batman Forever: Though a bit vague, Riddler seems to be doing this (or using other people's brainpower to amp his own mental function, or both.) It makes him a megalomaniac and a malfunction of the machine physically warps him.
 * The Butterfly Effect: thanks to Mental Time Travel, the hero suffers mental instability, migraines, and institutionalization when the doctors find out "he has four lifetimes' worth of memories in his head!"
 * Charly, an adaptation of the classic Flowers for Algernon, has an intellectually handicapped man undergo a treatment that boosts his intellect up to normal and then far beyond. Unfortunately, as he discovers from checking out the test rodent Algernon, it'll cause him to burn out and wind up even stupider than before, possibly brain-dead.
 * In Rain Man, Dustin Hoffman's character is an autistic savant who has superhuman memory retention and computational skills, offset by severe social disability; based on a Real Life person.

Literature

 * In Fred Hoyle's novel The Black Cloud, scientists communicating with the Cloud are given a recording of its knowledge. An initial attempt to download the knowledge into one of them proves to be quickly fatal; a second attempt seems more promising at first but also ends in mental breakdown and death.
 * The book Ender's Shadow, a companion novel to Ender's Game, features a very, very dark version of this trope. It is revealed about halfway in that Bean, a diminutive but fiercely intelligent kid, has been This remains a major plot point over the rest of the "Shadow" novels.
 * Worse, it's discovered that Bean's  Naturally, Bean and Petra go to great lengths to prevent   from being given   Equally naturally,   deliberately screws with their preventative measures.
 * In A Study In Scarlet, Sherlock Holmes claims that the reason he is so ignorant of such things as astronomy is that he's trying to save brain-space for forensic knowledge.
 * Terry Pratchett's Discworld series.
 * In Small Gods, the illiterate Brutha nevertheless has Photographic Memory. He experiences discomfort after visually memorizing the contents of an entire library. The discomfort comes from one of the recurring themes in the Discworld series: Knowledge is power. Knowledge is found in books. Therefore, libraries have immense power. And Brutha had all of one in his head, even if he could not read it.
 * While he doesn't have a brain in the biological sense, Death often finds his vast Photographic Memory to be a psychological burden. At such times, he tends to get drunk and/or go AWOL while Susan takes care of the family business.
 * In the James Allan Gardner book Radiant, the "Balrog" hive-mind spore colony infecting Youn Sue's mind grant her wish to see and think as they do... by spreading her mind slowly to absorb more information while retaining the detail of her original perspective. She pleads for them to stop, but they continue until she blacks out from brain damage. The Balrog then moves in and reconstructs the damaged bits to bring her out of her coma.
 * In David Brin's Kiln People, a widespread technology is the creation of "dittoes", short-lived clay-based copies of a person that share their knowledge and upload their memories into their original at the end of the day. The problem is that the human brain only has space for a few hundred years' worth of memories -- ordinarily not that big a problem, since over your lifetime you'd only add maybe a century or so of memories. One character, however, has become a "queen bee" -- she stays in one place and sends out dozens of dittoes at a time to live her life for her -- and arranges for an elaborate suicide when she realizes she's almost out of room.
 * Averted by the titular immortal of The Vampire Tapestry, who remains active for roughly one human lifespan at a time, then goes into hibernation for an undetermined period, always waking as an amnesiac.
 * In the novella Starplex, this is the cause of one species' (the Ibs) natural death--the crystals that store their memories become full, and new memories begin overwriting their autonomic functions. Other species, once they develop immortality, eventually have to start discarding portions of their memories once they reach a certain age, though it's not clear what the side effects of not doing so would be.
 * In Bruce Coville's My Teacher Is an Alien series, Duncan goes from dumb bully to super-genius after using an alien machine. However, his brain soon begins to pick up information like radio and TV signals out of the air, making it impossible for Duncan to think. Justified:
 * The Dark Templar trilogy of books from Starcraft has this as one of the main plot threads. Human archaeologist Jacob Ramsey gets the entire mind and consciousness of a Protoss transferred to him, except this Protoss is a Preserver, who has the memories of the entire race. This results in Jacob having several brain tumors develop, and he must find a way to get the Protoss out of his head.
 * A short story and script for several anthology series: a man invents a memory enhancement drug, but finds that the result drives the adult insane. A baby/young child takes the drug, and their developing brain adapts to the new load. As a result, the child becomes a rich genius and take control of his parents and then the world.
 * In Poul Anderson's World Without Stars, humanity has achieved near immortality, but because our brains weren't designed to hold centuries of memories, every hundred years or so, people have to go in and decide what memories they want to keep, and what they want to forget.
 * In The Ellimist Chronicles (an Animorphs prequel), Toomin (The Ellimist) is captured by "Father", a giant squid-like alien who connects his tentacles into the brains of his victims, and thus, having a network of hundreds of minds, has ridiculous intelligence (and the faculties to handle it). After decades of Father using Toomin as his plaything, Toomin finds a way to defeat him by absorbing all the thousands of minds that Father uses... into his one brain. The strain of having so many minds meant for so many body types caused him to hallucinate. Rather than finding a way to return to normal, however, he spends years building a spaceship/supercomputer to plug himself into (and escape Father's planet), which makes him capable of handling his newfound superintelligence. He is still mostly Toomin, however.
 * The Secrets of the Immortal Nicholas Flamel series has Gilgamesh. Yes, the Gilgamesh from the earliest written story. He has many millennia of memories, causing him to go slightly nuts and lose track of some of them; he talked with one person for five minutes before remembering he wanted to kill that person.
 * A Science Fiction story released in one of Asimov's anthologies had people suddenly going catatonic because the new invention of TV stored a memory for every frame shown on-screen, causing people to run out of storage space. The President, advised of the problem, held a live teleconference to warn people of the problem and froze up while watching himself on the monitor opposite him.
 * In Foundation and Earth,  is revealed to suffer from a bad case of this.
 * In a variant, Kate in The Long Dark Tea Time of the Soul once read that the human brain can juggle a maximum of seven trains of thought or observation at once. Sure enough, when an eighth thought occurs to her, a plot-relevant detail she'd just begun to notice pops out of her head and is forgotten.
 * In Time Enough for Love, part of Robert A. Heinlein's Future History series, this is noted as an issue when a computer seeks to download its personality into a Wetware Body in order to experience life as a human. The computer's mentor and confidant has to remind it that it won't have nearly the same processing power or capacity for information storage, and indeed once the feat is accomplished, the now-female human Minerva discusses the choices she made in terms of which memories to discard and which to keep in order to avoid this trope.
 * In Inheritance, is defeated this way.
 * The Bruce Sterling short story Our Neural Chernobyl is written as a review of a monograph studying the social and cultural effects on the world after an engineered virus is released that causes rampant dendritic growth - essentially, making people's brains extremely plastic and adaptive so they can constantly learn and think at faster and faster rates. It also frequently causes lethal burnout, nicknamed "chernobyling" after the Chernobyl power plant disaster in the '80s. Eventually, the virus even jumps species, with some animals showing signs of increased yet distinctly inhuman intellect.
 * A character in M. John Harrison's Viriconium stories can only remember the last two centuries of his life, although evidence suggests he is far, far older. He lives in a vast underground complex full of machines he doesn't remember building -- or what they do -- and entire wings he forgot existed.
 * In the book Flowers for Algernon, the title-giving mouse and protagonist Charlie Gordon both are given extreme intelligence from an operation. However,.

Live Action TV
""Make them stop! They're everywhere. Every city, every house, every room; they're all inside me! I can hear them all and they're saying... NOTHING! GET UP! Please, get up!... Please God, make me a stone.""
 * Stargate used this a few times:
 * In Stargate SG-1, there are Ancient Repositories, where if you stick your head in you get all the (possibly nearly infinite) knowledge of the Ancients, but a human mind will slowly degrade for as long as the information is still in there. Jack O'Neill got nailed twice by those devices -- and only the fact that he has the Ancient gene allowed him to survive very long in the first place.
 * Only the fact that he has the Ancient gene allowed him to receive the knowledge in the first place. Notice how the Repositories only really react to him, and other ATA Gene carriers.
 * Also in Stargate SG-1, Orlin, an ascended Ancient takes a human body in order to help the main characters with the current Big Bad. Unfortunately, he holds onto the necessary knowledge for too long; he ends up suffering massive brain damage, and has to be institutionalized.
 * In Stargate Atlantis, a hyper-evolution machine gives Rodney McKay amazing mental powers (including psychic ones such as mind reading and telekinesis) - but at the cost of it eventually killing off the part of his brain that controls the lower functions such as his heartbeat. It's at the last moment of his life that he manages to figure out (using his amazing intellect) how to reverse the process to return to normal.
 * This almost happened to Max in an episode of Dark Angel which involved her taking a rival series clone's neural implant and installing it into her own brain. The strain nearly burnt out her nervous system.
 * Doctor Who
 * Russell T Davies is clearly very fond of this -- back in the 1st series finale, Rose absorbs the time vortex, making her effectively a goddess, but is in danger of being "burned up" by the power and whispers, "I can see everything. The sun and the moon, the day and the night -- but why do they hurt? My head... is killing me."
 * In "Forest of the Dead"
 * Though it doesn't seem to be actually dangerous, in The Second Coming Steve (played by future ninth Doctor Christopher Eccleston), discovers that he's the literal son of God, and compares the experience of accessing divine omniscience with a human brain as like "downloading fifty-million megabits into a pocket calculator," and admits that it hurts.
 * Lt. Barclay in Star Trek the Next Generation episode "The Nth Degree", although the newly gained super-intelligence doesn't seem to be dangerous in itself. The problem comes when he connects his brain directly to the ship's computer. He uploads himself and uses the extra processing power to expand his intelligence, but then realizes that his brain alone would be too small to contain it, so he's stuck in the computer until the end of the episode.
 * On Andromeda, Harper had a database downloaded into his brain (he has a computer port on his neck), and it played out similar to SG-1, only instead of being directed to a single goal like O'Neill, Harper began and abandoned dozens of projects.
 * Married With Children featured a low-grade version of this in at least one episode: Kelly Bundy was capable of learning new things, but there was only so much room inside her brain, and for every new piece of info that finally got pounded in, something else got pushed out. The episode centered around training Kelly for a quiz show... and by the time Bud was done with her, she'd forgotten what a doorbell was.
 * And at the climax of the show, a short film overwrote the answer to the last question... which was about a sports accomplishment of Al's.
 * In the Buffy the Vampire Slayer episode "Earshot", where Buffy accidentally gets telepathy, she starts hearing everyone's thoughts all the time. This not only overwhelms her, but it will inevitably cause her to go crazy unless the telepathy is removed. There was one other person to have gotten this, and he ended up in complete isolation, away from any other people.
 * In Heroes, Matt Parkman has this problem when he gets his telepathy, but after a while he learns to control it better and the problems stop.
 * Joan of Arcadia had an episode where a child Joan had babysat earlier in the season died. In the middle of a Rage Against the Heavens rant at God, God offers to show her what he sees and hears every day. Fifteen seconds later, she's on the floor, unable to deal with the downsides of omniscience.
 * Cordelia from Angel is given the "gift" of visions that turned out to cause her brain to slowly deteriorate since humans weren't meant to have them. She keeps it secret for years before slipping into a coma and learning that she will eventually die from this if she doesn't agree to become half demon to compensate. She is also shown other examples of what happens because of the visions: one girl whose head literally blew out the back, and an alternate-universe Angel who was driven completely insane by them.
 * Firefly's River Tam got along pretty well being incredibly intelligent with a bit of psychic ability. Then the government gets a hold of her. They make her undeniably kickass, but one consequence is that now her greatly increased psychic abilities make her insane, unable to filter out what she hears.
 * Firefly's River Tam got along pretty well being incredibly intelligent with a bit of psychic ability. Then the government gets a hold of her. They make her undeniably kickass, but one consequence is that now her greatly increased psychic abilities make her insane, unable to filter out what she hears.


 * Chuck entirely averts this
 * And then, there's the instances where characters aside from Chuck gain the Intersect.  Keep in mind, that these instances involved variations of the Intersect that were tampered with "trojan horses".
 * And even moreso of Dead At 21, in which the hero has one year to keep the intellect-enhancing chip in his brain from frying it.
 * In Red Dwarf, episode "Holoship", Rimmer has all the knowledge and experience of two officers of the ship transferred into his own mind so as to pass an exam. Kryten warns him, however, that it could "reduce him to a gibbering wreck". It doesn't, and the result is slightly unnerving.

In another episode, the ship's computer Holly finds a way to boost her intelligence and undo three million years of "computer senility". Overclocking it, she gets an IQ of 12,368 (over her original IQ of 6,000) at the cost of reduced run-time: about 3 and a half minutes.
 * On one episode of Scifi's The Invisible Man, Hobbes was accidentally stabbed with a serum that would cause his intelligence to rapidly increase. However, he'd go through several stages, gradually becoming an Insufferable Genius, then a crazy genius, then, with this trope, his brain would become so advanced he would retreat into his own mental world of absolute knowledge, and stop using or caring about his body at all. Fortunately, it was stopped and reversed at the Insufferable Genius stage.
 * The college students who were injected with the serum eventually realized that life is pointless and committed suicide. Unfortunately, one of them took the creator of the serum with her.
 * Star Trek Voyager: Seven of Nine downloads huge amounts of data straight into her head, but can't handle it, and starts creating wild conspiracy theories.
 * The scary thing is how much sense most of them make, given the evidence she provides.
 * An episode of Amazing Stories, "One for the Books", had a man involuntarily soaking up all the knowledge contained in the library in which he worked, which quickly drove him towards madness. In the end.

Video Games

 * In Wizardry: Bane of the Cosmic Forge, one NPC is a moderately evil wizard who wished on the Cosmic Forge that "I shall know everything." The artifact's solution to the trope was to split him into two consciousnesses and divide the knowledge between them. However, as it chose to concentrate data in the one that got the body, he went insane anyway. The one who got the understanding (the "hows" and "whys") relates the story to your party.
 * It has become an open secret that that Arakune of Blaz Blue Was Once a Man, but a good portion of his dementia comes from a Runneth Overing Skull.  This makes all the attempts to save him with The Power of Love more tragic.
 * Final Fantasy XIII-2 - and  will experience a vision of the future every time . While that may sound alright, each vision effects them worse and worse (it begins as a small migraine, and eventually causes them to faint each time) until they

Web Comics

 * Mindmistress gets her super-intelligence from a Phlebotinum pulse that kills the target in two weeks unless reversed (the brain grows so much that it is analogous to brain cancer). Her non-super self is mentally challenged.
 * Also used in a different way in a later story, where the villains of the week attempts to steal her knowledge. They all go insane -- the human mind cannot handle that much knowledge.
 * Forthought is an ordinary man who underwent the same process. He is considerably smarter than MM and with his more advanced mental capacity he wills his brain to not have cancer rather than transform back.
 * Homestuck - Sollux is a high-level psionic. The mind honey which boosts his lusus from idiocy completely overloads his brain when he eats it. . He recovers, but there are terrible consequences.
 * In Schlock Mercenary a race of Immortal aliens are found on a backworld planet. The collapse of the civilization nearly a million years ago was due to their experiments with immortality, specifically replacing the brain with a super-efficient computer version. Many went insane due to too many days going by too similar for the mind to sort out. The survivors installed Selective Amnesia so that they would not go mad.

Web Original

 * Apparently, this is what happen to humans coming in contact with the mysterious being SCP-606 residing at the SCP Foundation, resulting in coma and death from overload of information. The entity doesn't seem to do it out of malice, instead calling it "enlightening" its victims.
 * During the Happy Hour arc of I'm a Marvel And Im ADC, an Exposition Beam is weaponized to do this on a small scale.
 * In the Global Guardians PBEM Universe, this effect is one of the many reasons why 75% of all mentalists end up going stark raving mad.

Western Animation

 * Code Lyoko example: Jérémie once tried to use the same quantum memory technology that powered the Supercomputer to enhance his own brainpower. Of course, it backfired due to both the immense physical strain and the fact that XANA introduced the possibility of that maneuver as a Red Herring.
 * In an episode of the Men in Black animated series, aliens bring to Earth a "Cerebral Accelerator" that boosts human intelligence. Agent J tries it on before MiB has a chance to safety-test it for side-effects and learns the device gives him Ripple Effect Proof Memory but will eventually make his head a splode.
 * The episode of Jimmy Neutron Boy Genius where Sheen, who is somewhere between The Ditz and a Cloudcuckoolander, is hit with Jimmy's brain-gain helmet, without fixing the issue of the original brain-drain helmet, a limiter. Sheen gets outstanding Psychic Powers, an A God Am I complex, and a head the size of a house before the Reset Button is hit.
 * At one point, Jimmy calculates the maximum possible number Sheen's IQ could grow to. It hits infinity.
 * This is used against a villain in one episode of Darkwing Duck. In the final showdown, DW and Launchpad get their hands on the Norma Ray, a device that increases your IQ as long as you clear your mind of all thought (but gives the user the nasty side effect of having a literal and figurative "swelled head"). They bombard the villain with rays while asking him a bunch of tough questions at once, causing him to lose his concentration and make his head so big that it blows up.
 * Not just IQ. The device also gives you ridiculous Psychic Powers, ranging from prescience to manifestation (Launchpad materialized a giant fridge out of thin air).
 * Happens to Spongebob SquarePants of all people, in the episode Squilliam returns. Squidward turns the Krusty Krab into a fine dining establishment to impress Squilliam, and Spongebob is to wait tables. After learning everything associated with fine dining, his skull runneth over badly -- he cannot even remember his own name any more! The only thing he can remember, except for fine dining, is breathing.
 * Not sure how cartoon sponges operate, but most creatures don't need to remember to breathe, it's automatic (autonomic?).
 * In The Batman, Dr. Strange gets all the knowledge in the universe in return for helping  - when he receives it, he ends up comatose (though The Martian Manhunter can still read his mind to get the information they need to defeat  )
 * In Xiaolin Showdown, using the Shen Gong Wu named Fountain of Hui grants the user insight to anything and everything. However, without its sister-Wu the Eagle Scope, which is mostly an uber-telescope, the Fountain of Hui will only grant the user a humongous head and random facts, such as the length of the world's largest toenail, which they will babble incessantly for about a week.
 * It also seems to be imply that using the Fountain of Hui without the Eagle Scope results in pain accompanying the above huge head and random facts spouting given that Omi's immediate action after saying the length of the world's largest toenail is to grip his head and complain "Ow…"
 * In X Men Evolution, Rogue's power absorption eventually left her with fragments of all the people she absorbed, such that she couldn't help randomly using their powers occasionally. Then she went and bumped into Mystique, providing a handy outlet for those fragments in the form of shapeshifting. A rampage ensued. Xavier had to telepathically purge her of all the accumulated personalities to get her back under control.

Real Life

 * People with bipolar disorder often go through a period of high creativity, fast and often quite clever thinking before the sleep-deprivation psychosis kicks in. The feeling of being on such a high can often be like one's skull literally overflowing with energy; and sleep deprivation doesn't need to happen. The insomnia can be controlled with medication, for a start.
 * Also people with Eidetic Memory can set off a memory at any time by some random thing, be it good or bad.
 * Subverted by people who have suffered the loss of a substantial portion of their brains, due to strokes, tumors, accidents or surgery, yet continue to function and accumulate memories normally throughout their lives. Even patients who have entire cerebral hemispheres removed to halt their epileptic seizures don't "run out" of memory-space, despite having only 50% storage capacity.
 * In either Ripley's Believe It Or Not, or Guinness Book Of Records, there was an account of a girl who at age 14 had learned fluency, and was writing papers in about twelve different languages. She ended up dying at about age 16 (possibly from a seizure).
 * Certain kinds of autistic patients known as savants make up for their seemingly handicapped social skills with superhuman computational ability.
 * Solomon Shereshevskii, a Russian mnemotist (who did not, in fact, have an Eidetic Memory) had the ability to remember things so well that he became dislocated in time; he eventually became unable to tell whether the thing you just told him happened 5 minutes or 5 years ago. He had to literally learn to mentally remove facts from his memory (in other words, deliberately forget). It didn't help that he had fivefold synaesthesia, an extremely strong form of synaesthesia in which stimulating one sense meant a reaction from them all. That Other Wiki has an article on him.
 * One of the theorized causes of old age dementia is that your brain reaches its effective capacity, and then stops working properly.
 * This is supported by the behavior of computers that are built to mimic neural architecture and then overloaded with data.