Only Smart People May Pass

""He has figured out Monsieur Adell's greatest weakness: His inability to think.""

- Tink, Disgaea 2: Cursed Memories

This refers to any barrier that requires the heroes to solve some kind of puzzle or Riddle Me This in order to pass. Alternatively, it could be some test of skill. Often given by Threshold Guardians (especially if the guardian in question is a Riddling Sphinx). You must be able to work it out based on the clues you are given on the spot. (If you must come to it with some knowledge, it's Only the Knowledgable May Pass.)

One wonders why this was deemed a better barrier than say, a lock and key carried on someone's person instead of being in a chest elsewhere in the building.

If the goal was to actually allow smart people to pass, like into Mensa, then this would make sense. But it's often a defense against smart people who want to take whatever is being guarded. If evil, these smart people will either already be past this puzzle or trick the heroes into solving the puzzle for them.

See Block Puzzle, the various Stock Puzzles and Stock Videogame Puzzles, and Solve the Soup Cans for examples of this. Expect even the least smart of protagonists to be able to find a way to solve what was supposed to be an ingenious puzzle.

This trope dates back to at least the Sphinx in Greek mythology, making it Older Than Feudalism.

Compare Only the Worthy May Pass, These Questions Three; also see First Contact Math, and contrast Only Idiots May Pass.

Anime and Manga

 * The Door test from Tower of God does a subversion on this: It is indeed possible to figure it out when you are really smart, but it's also possible if you are a gambler, faithful or indifferent. The objective was merely to open any of 12 doors in five minutes, but one wasn't told that. One was told one had to open the right door in ten minutes and that the wrong choice would lead to one's death.
 * The lower levels of Mahora Academy's Library Island in Mahou Sensei Negima is filled with these, as Negi and the Baka Rangers found out the hard way in an early chapter. However, these were deliberately placed by the headmaster, who appears to have plotted the whole adventure to force the Baka Rangers to study for their finals. The characters treat it more like Alphabet Soup Cans though.
 * An episode of Ojamajo Doremi has Doremi (of all people) answer a somewhat-Sphinx inspired riddle.
 * Spoofed in Gash Bell with Poosophagus (Unko Tin Tin). He guards Faudo's esophagus and threatens to drop the whole party in stomach acid if they don't all get a question right. Fortunately, most of his questions are really easy, when he remembers to ask one at all. He only asks two hard ones:
 * 829,735 X 962,527 = ?. Posed to Kiyomaro, a supergenius who calculates the answer in his head. ("It's 797,812,605,345!").
 * Prove Fermat's Last Theorem. A question that would be impossible for almost anyone on the planet, this was posed to Umagon, who can't even speak. Kiyomaro forces Poosophagus to give Umagon an easier question, a more conventional riddle. Mainly, because Poosophagus didn't know the answer himself.
 * Subverted in Princess Tutu. After a mysterious spirit kidnaps Mytho, Ahiru races to find him—and is asked riddles along the way. Ahiru, being an Idiot Hero, gets them all wrong, but it turns out that the voice wasn't testing her, but telling her who it was--.
 * Subverted in Azumanga Daioh when Tomo is asking complicated puzzles requiring lateral thinking. Class genius Chiyo is stumped by them, but class space cadet Osaka answers them all without any hesitation.
 * There's a manga in which in order to gain admittance to a certain building, a character was asked a math question by the building's owner. The character laments that she's bad at math and blurts out a random (wrong) answer. In a subversion, the building's owner lets her in since it turned out that he wasn't looking for the answer: he asked the question in a certain dead language, and the fact that the character understood that she was being asked a math problem proved that she knew the language.
 * In a completely justified example, the entrance exam in Detective Academy Q is filled with this sort of thing.
 * One of the Hunter Exam trials in Hunter X Hunter asks you who you'd choose to save, your mother or your lover. When Gon notices the first guy (who chose the mother) was sent to his death, he realizes no answer is right, and says nothing. Again, no answer is right. They pass.
 * In Summer Wars Kenji solves a 2056 Bit encryption not only on paper but in his head in under a minute to stop Rogue Ai Love Machine.

Film
""But isn't green!" "You can paint it green." "It doesn't hang on the wall!" "You can nail it to a wall." "But doesn't whistle!" "Oh, come on. I just put that in to stop it from being too obvious.""
 * The "Bridge of Death" scene (These Questions Three) from Monty Python and the Holy Grail savagely parodies this trope.
 * Indiana Jones and the Last Crusade: The Knights of the Grail have protected their treasure with a series of tests, each more fiendish than the last, to ensure that no unworthy man may pass. The tests are multi-layered: to prove worthy, one must find the clues to the tests elsewhere, interpret them correctly, and successfully act on the interpretation. Without the clues (which Indy's father found in his decades of research into Grail lore) it would be considerably harder if not effectively impossible to figure out the traps before they killed you.
 * Those Wacky Nazis try to beat it with Trial and Error Gameplay - given that Nazis really aren't all that smart, they've already lost over a dozen people to the first trap by the time Indy shows up.
 * "Get another volunteer."
 * Worth noting that a child or a midget (shorter than the blades height, light enough to step on the loose tiles and with a different prospective for the hidden bridge) would have passed effortlessly.
 * The tunnel leading to One-Eyed Willy's ship in The Goonies is filled with many booby-traps, the most memorable a musical riddle. Which actually makes sense, since during Willy's time, only people with a noble/high-born education would actually be able to read sheet music - even most actual musicians would only know how to play instruments, not read standardized notation.
 * The sphinx guarding Giants Orbiting in Mirror Mask refuses to let Helena and Valentine through without answering riddles. However, as this is by Neil Gaiman, Helena's answer to the "4 legs in the morning, 2 legs in the afternoon, 3 in the evening" riddle was one of the performing dogs at her parents' circus, who walked around on his back legs as part of the afternoon show and hurt his paw partway through. Her counter-riddle was, "What's green, hangs on the wall, and whistles?" Answer:.


 * In Labyrinth Sarah solves a classic Knights and Knaves puzzle. She can only ask a single question to one of two characters, one of whom always lies and the other tells the truth. She asks one what the other would say and gets a reliably false answer.

Gamebooks

 * Constantly in Lone Wolf, where all your enemies use number problems to protect their stuff. In a gamebook with numbered sections, of course, number puzzles are the easiest to implement, and leave little possibility of cheating for the player. Which made the page randomization given to some editions especially stupid.

Game Shows

 * Often used when giving away prizes to make sure that it's "skill based" rather than luck based, even if it's effectively luck based. Generally the question is very simple, allowing anyone to answer it. There are entire shows based around this which intend to collect money from unwary viewers via premium-charged phone or SMS, giving away only a token prize for the winner. Another possibility is to make an "unsolvable" puzzle, such as "count the money in the picture" (when the answer is finally shown, it is revealed that there were coins in the picture completely obscured by other coins) or "find the names of 3 bands in the letter square" (which is filled with misspelling of popular band names and the answer is 3 obscure bands with nondescript acronym names). Multiple callers can attempt to answer but generally none will succeed, so nobody gets the prize because they weren't "smart" enough.
 * In some places (Canada, for example) the law prohibits "gambling" (e.g. a lottery, even if no entry fee is charged) but permits "contests of skill". Apparently, correctly answering "2+2=?" makes it a contest of skill as far as the law is concerned, even if the actual winner is then randomly chosen from the correct entries (i.e. all of them). To be fair, I don't know if the law is actually written in such a technical and boneheaded way, or if this is a cargo cult solution to a nonexistent problem by marketroids who assume it is.

Literature
"She struck the door and spake thusly: "Open up, you little sods!""
 * In How Kazir Won His Wife, a king sets his daughter's suitor Kazir puzzles in order to assess his intellect. If Kazir fails, the king will not permit his daughter to marry Kazir.
 * Harry Potter:
 * In Harry Potter, Dumbledore banks on these to hinder Voldemort from getting to the Philosopher's Stone. Most of the puzzles placed to guard the Stone aren't actually puzzles (rather than leave a spell to ask you how to defeat Devil's Snare, Dumbledore let Professor Sprout decide that it would be much more effective to just set the plant on anyone who came through); notably, the exception is Snape's logic puzzle with the potions: "Most wizards haven't got an ounce of logic; they'd never get out alive."
 * Also, to gain entry to the living quarters of the House of Ravenclaw, one must answer a intellectual riddle. Of course, this seems to be designed to help the Ravenclaws increase their intellectual capacity, so it's literally "only smart people may pass".
 * This has the unfortunate side effect of allowing anyone smart into the Ravenclaw House (and, at least potentially, keeping Ravenclaw members themselves out part of the time), while the other three houses rely on more conventional methods of ensuring that only their respective house members are allowed to pass, making them more secure. Brilliant choice, Smart Guy House.
 * Although this does manage to lock the Carrows out of Ravenclaw dorm during the last book, until they found someone who was not an idiot to let them in. In fact, the Carrows, being Deputy Heads, probably had free reign of the rest of the school, including knowing the various dorm passwords, but would be unable to do that with the Ravenclaws. So all in all, a logic puzzle worked out pretty well for Ravenclaws, especially considering that people manage to break into both the Slytherin and Gryffindor dorms simply because their students do not have a very good grasp of password security.
 * In the fourth book Harry stumbles on a sphinx in the labyrinth and has to solve its riddle.
 * In H. M. Hoover's "This Time of Darkness" the main character has been an outcast because she is literate, in a world where people are trained from childhood to be stupid and ignorant. When she comes to a locked door containing a clearly written explanation of how to open it and disarm the guard lasers, she realizes with horror that whoever put the door there intended to kill anybody who went through who couldn't read - that is, if * anybody else* went through the door, they'd be killed.
 * In The Mote in God's Eye, the alien Moties have museums that are locked using astronomical puzzles. This is Justified Trope, since the museums are meant to help restore their civilization after the Dark Ages caused by inevitable, unstoppable population explosions.
 * A variant occurs during The Dark Tower series, when Blaine,  voluntarily takes the heroes to their destination, but agrees to let them live only if they can come up with a riddle he cannot answer. The catch is that Blaine has
 * One of the gadgets used by the mysterious V.F.D in Lemony Snicket's A Series of Unfortunate Events is the "Vernacularly Fastened Door", a lock which can only be opened by answering trivia questions.
 * To be fair, it is a theme of the series that the good guys are more well-read than the bad guys.
 * This happens in effectively every single book in the Redwall series. It seems as if every single protagonist, post-book, develops the same degenerative brain disease that compels them to entrust some awesome Plot Coupon to a future generation of the abbey via a long series of puzzle riddles. Instead of just locking it in a vault and passing down the key. This tendency was sent up in an xkcd strip.
 * Subverted and parodied in Roger Zelazny's second Amber series. Merlin encounters a Sphinx that will eat him if he can't guess the answer to a riddle. Merlin gives a plausible answer, but the Sphinx is looking for a specific one (that is virtually unknowable, relating to a then-obscure aspect of the story's world). Merlin argues with the Sphinx, eventually getting the concession that the Sphinx will let him pass if he can come up with a riddle the Sphinx can't answer. Merlin does so, with "What's green and red and goes round and round and round?" . This is echoed in a later book when another guardian refuses to use this sort of test, but just for fun asks a riddle anyway—and it's the same one Merlin posed.
 * The Riddle Game in The Hobbit. To be fair, Gollum's kinda nuts.
 * Then there's the in-universe debate on whether Bilbo technically cheated. It was concluded that "What have I got in my pocket?" shouldn't have been counted as a riddle at all, but it's arguably fair if Gollum chose to try to guess it anyway, which he did.
 * Fellowship of The Ring subverts this with the gates of Moria; what's taken to be a riddle is just a literal instruction, although knowledge of Elven script is required to know that there is a password at all.
 * Tolkien's door gets a Shout-Out in Terry Pratchett's Witches Abroad:


 * Deconstructed in Diamond Dogs by Alastair Reynolds. The novella concerns the discovery of a sealed alien tower that can only be ascended by answering successively more difficult math problems in various chambers. The characters in the story are eventually forced to augment their own intelligence with Neural Implants just to proceed. More sinisterly, the doorways between each chamber get smaller each time, forcing the characters to also modify their bodies to fit. The deconstruction comes when narrator realizes that the Tower probably doesn't have anything at the top. It exists solely to goad gullible intelligent species into exploring it. When they get to the top, the tower "harvests" them like a Venus Fly Trap. The story is also a subversion, as we never find out for sure whether there is anything at the top of the tower; the narrator decides that he'd rather not sacrifice (any more of) his humanity just to get to the top.
 * Allen Steele's Labyrinth of Night features an alien complex on Mars entered through a series of locked doors with puzzles that require increasingly more intelligence to solve (and still-active death traps for the unwary). The archaeologists were baffled by the last chamber, which just played music, until they brought in a musician to jam with it, proving we have culture as well as brains.
 * In the Polish children's book Satan From The 7th Grade, protagonist Adam follows the clues and riddles that a Napoleonic-era soldier left for his brother, to find where he hid the treasure he brought back from the war. The attempted justification is that the soldier picked things only his brother would know, such as the book they read together when they were studying Italian.
 * Pick a Deltora Quest book. ANY Deltora Quest book. Chances are you'll find a riddle that needs solving, some cryptic code that needs cracking or some other puzzle that needs figuring out.
 * Probably more than one.
 * Dan Brown attempts this in The Da Vinci Code. Unfortunately for readers with a functioning brain, these include such gems as the "strange script" of an unrecognised language that a symbologist, the granddaughter of a da Vinci expert and another da Vinci expert spend about five pages puzzling over. Two pages into this sequence, there's a copy of it printed—it's in da Vinci's trademark mirror writing.
 * From Alice in Wonderland by Lewis Carroll: "Why is a Raven like a writing desk?" Lewis Carroll himself wrote: "Enquiries have been so often addressed to me, as to whether any answer to the Hatter's Riddle can be imagined, that I may as well put on record here what seems to me to be a fairly appropriate answer, viz: 'Because it can produce a few notes, though they are very flat; and it is nevar put with the wrong end in front!' The canonical answer, of course, is; " " Despite Word of God, people keep trying to "answer" the riddle. Some of the more famous "answers" include:
 * "Because there is a B in both and an N in neither."
 * "Because they both have inky quills."
 * "Because Poe wrote on both."
 * Another answer, in "The Cheshire" by Bill Kte'pi. The Genre Savvy titular character
 * Yet another, from a Christopher Stasheff book:  Naturally, this hasn't been a really valid answer for some time.
 * An annotated version of Alice in Wonderland suggested "It stoops with a flap," or a flap of wood that creates an incline on which to write.
 * Another answer: It just seems to fit Wonderland so very well.
 * The Crown of All Things in The Last Watch was sealed in a most ingenious manner, but Merlin thoughtfully left a rather clever riddle behind. This was Justified in that providing a hint was part of Merlin's idea of fair play, and it later turned out he had a very good reason to make it possible for someone intelligent to get their hands on it.
 * Sort of a subversion: in Romance of the Three Kingdoms, Cao Cao is fond of word games, including leaving instructions in the form of incredibly involved plays on Chinese characters. The only problem was that the guy who solved them, Yang Xiu, made Cao nervous, both for his intelligence and for supporting one of Cao's younger sons rather than Cao's chosen heir.
 * Doubly subverted in Piers Anthony's novel Macroscope. The "Destroyer Signal", a radio signal picked up by a SETI search, appears at first to be a treasure trove of alien scientific knowledge that a few of the smartest humans may be capable of understanding, but turns out to be designed to overload their brains and burn out their minds with too much knowledge. Later in the book, though, it turns out that it is actually an "only good people may pass" test, designed to destroy any intelligent mind not belonging to Perfect Pacifist People, to prevent all the tech (especially FTL Travel) from falling into the wrong head.
 * In the short story "The Most Precious of Treasures" by Desmond Warzel, the protagonists must solve a room-sized Queens Puzzle in order to pass from one room of a dungeon to the next. A completely straight use of the trope, as the point actually is to allow smart people to pass. Its actual purpose is to allow people in and keep beasts out, thus it's really a case of Only Sentient People May Pass; the implication is that the builder chose a well-known puzzle on purpose.
 * In Star Trek: Typhon Pact (part of the Star Trek Novel Verse), the home and office of the Tzenkethi Coalition's Autarch is inside a building with a flexible and highly changable design. To access the house requires contemplation of mathematical principles and aesthetics, to puzzle out the likely position of concealed openings. Agents of the Autarch are therefore tested every time they report to the building, and must demonstrate their worth by finding a way inside.
 * In the novelisation of Earthsearch II, the puzzle at the climax is extremely simple but highly effective:
 * Terry Pratchett has a lot of fun with this trope in Pyramids. Pteppic meets the sphinx of Greek mythology—and gets into a three-page discussion about how the classic riddle ("What is it that walks on four legs in the morning, on two at noon and on three in the evening? -- A man") doesn't actually make a lot of sense. The final version: "What is it that, metaphorically speaking, walks on four legs for about twenty minutes just after midnight, on two legs for most of the day (barring accidents) until at least suppertime, after which it continues to walk on two legs or with any prosthetic aids of its choice?"
 * Septimus Heap has the Wright of the Widdle in Queste, where the protagonists have to guess the meaning of some expressions that refer to some symbols to enter the House of Foryx.

Live Action TV

 * The first episode of Are You Afraid of the Dark??, "The Tale of the Phantom Cab": The woods are haunted by the ghosts of lost hikers and campers who found Dr. Vink's cottage. He would send them to board the Phantom Cab and die in a replica of the same crash that killed the driver. Why? Because none of them (until the two boys in the tale) could answer his riddle: "What has no weight? Can be seen with the naked eye? And if you put it in a barrel, it will make the barrel lighter?"  Other common entities that satisfy this description: fire, "A flashlight beam."
 * Stargate Verse:
 * A simple geometry fact question - not a problem, even, just being able to identify the first six digits of pi and the radius of a circle - guarded an Asgard communication device that would have allowed the populace of a world to speak with their "god" and learn all kinds of things about the Universe in Stargate SG-1. Sort of justified in that Thor didn't want to speak directly with a society until they achieved some kind of scientific knowledge. The Ancients, or at least Merlin, were also fond of using these to guard superweapons.
 * The Asgard made a few boo-boos with their test, though. 1: The native that the SG-1 members brought with them (for whom the test was presumably designed) didn't recognise the inscribed runes as numbers, only as letters. It was only Daniel who knew that they were once also used as numbers. 2: In order to divine the inscription's (presumably) correct meaning, the team had to use a large amount of artistic license to improperly fudge numbers from a base-19 absolute numbering system (the runes), into a base-10 positional number system (what we use on modern-day Earth), AND figure out that there should be a decimal point in there. 3: To indicate an understanding of the inscription's meaning, Daniel could have indicated either the diameter of the circle, or a square with sides the length of the circle's radius. Instead, he indicated the circle's radius alone. But hey, it's still a cool concept.
 * In "The Tomb", a ruined temple to the Goa'uld Marduk was blocked by a great stone door inscribed with the Babylonian creation myth. Opening the door required pressing the sections of the text that were incorrect, things that in theory only the priests of Marduk would know. Fortunately Daniel Jackson has studied Babylonian mythology and reads the language.
 * The Dakara Superweapon, built by The Ancients, capable of wiping out all life in the galaxy, requires only the most basic understanding of Ancient language (two people who had never studied the language solved it by using someone else's notes). All you need to do is arrange letters so they don't form gibberish anymore, and ta-daa; the most powerful weapon in two galaxies is yours! Hey, there's a reason why the Ancients are considered to be the exemplar for Neglectful Precursors.
 * Also used during the quest to find the Sangraal. The team had to use four virtues, among them wisdom (in the form of solving riddles) to reach the Sangraal.
 * Stargate Atlantis isn't free from jumping through the intellectual hoops either - they just have to do it less often. Such as finding the ZPM by using the numbers 1-9 to make a magic square, part by desperation, part by realizing the significance of the number 15.
 * Doctor Who:
 * "42" has a bunch of locked doors that require trivia questions to open. In theory this is a passcode system, not a puzzle—the crew of the ship in question set the questions with the intent to be the only group who could give all the right answers. Notably, one of them set his favorite color as an answer. However, "the crew's changed since we set the questions," they may have been a little drunk at the pub quiz they got the questions from, and some of them had died horribly, explaining the fact that all the questions aside from the guy's favorite color apparently have to be answered by the Doctor or Martha.
 * As does the Tomb Of Rassilon in The Five Doctors. "Easy as Pi!" Granted, this episode is set far enough in The Future that a question referencing The Beatles is listed in the category of "Classical Music". It should be noted that the "Easy as Pi" puzzle seems to have no actual real world solution. The Master just strolls across the board initially and the Doctor's solution lacked any explanation.
 * "Death to the Daleks" has a test which takes the form of a series of death traps, killing anyone not smart enough to find the solution quickly. The goal of this is to select smart people... so they can be killed. Apparently, only nobody may pass. What was the point of the tests again?
 * "Pyramids of Mars".
 * The Hartnell-era story "The Daleks' Invasion of Earth" contains a particularly nice (or nasty?) example. Human captives of the Daleks are imprisoned in cells aboard their ships. The Doctor examines the door-locking mechanism and works out a way to deactivate it and thus escape.
 * The Cybermen do something similar in the Troughton-era "The Tomb of the Cybermen". Anyone skilled enough in symbolic logic to get into the tombs
 * In Babylon 5, an alien probe promises to transmit its vast store of knowledge to any species that passes its intelligence test.
 * Parodied brilliantly in the "talking frog" scene of The Tenth Kingdom. "One door leads to safety. One door leads to a horrible death." The heroes then find a new solution...
 * Parodied again in The Office, where Dwight keeps asking Ryan one logic riddle after the other. Ryan answers them so quickly that Dwight barely has the time to say the first few words before he gives the correct answer.
 * A staple of Knightmare.
 * Subverted in Double the Fist. The Womp has to get past a pair of "one always lies and the other tells the truth" guardians, but he's Too Dumb to Live and when the increasingly frustrated guards try to explain how the puzzle works the liar accidentally tells the truth, causing his head to explode.
 * A common task found on The Amazing Race.
 * This happens on Noel Fielding's Luxury Comedy, when Fantasy Man and Chief Woolabum want to cross the river but are stopped by a schizophrenic flag named Bobbatron, who demands the answer to a mind-bogglingly bizarre riddle: Naturally they Take a Third Option, pushing Bobbatron into the river and crossing the bridge as if nothing had happened.
 * One episode of The Monkees had them playing out a fairy tale. Peasants Mike, Davy, and Mickey are seeking Peter, and come to a castle guarded by a monster. It asks, "What has six arms, six legs, and a very short life?" Mickey promptly replies, "Three dumb peasants." The monster acknowledges that's correct and lets them inside, where the villain's guards are waiting for them. So the answer was right, but only not-so-smart people would want to pass.

Newspaper Comics

 * In Prickly City, Carmen is assured only the smartest people are allowed in an exclusive club.

Tabletop Games

 * Exalted:
 * Only Really Smart People may pass.
 * Exalted later plays it straight and justifies it in Under The Rose, which has a section of puzzle-based deathtraps designed by Autochthon, the Great Maker. A side-note mentions that as part of his inhuman mindset, Autochthon is physically unable to design any form of defenses without including puzzle-based deathtraps.

Video Games
""I mean, does he [Atrus] not mind people breaking in as long as they have an IQ of 150 and brilliant abstract logic skills? No wonder this place is always being smashed up by twisted geniuses seeking revenge on the entire family...""
 * Discworld Noir looks like it's headed for this when an ancient guardian wants to ask you a riddle to see if you are worthy to receive the McGuffin. Then come the subversions, first by the guardian who happened to forget the riddle during his 400-year-wait (but still insists to only hand the item to those who answer it) and then by Lewton who points out that someone of the unworthy faction would just hack the weaponless guardian to pieces. As he's in somewhat of a hurry, he gives the guardian the option to hand over the McGuffin - or he'll just pretend to be unworthy enough...
 * The guardian relents.
 * Happens a couple of times in Rogue Galaxy—most notable was the gigantic (as in, the size of a skyscraper) Block Puzzle, which the Big Bad had genetically engineered a person specifically to solve. And he still failed. Enter The Messiah... As a side note, that may be the only Block Puzzle in history to have its own dramatic Latin choir.
 * Shows up in an irritating section of Super Mario RPG on the SNES. While slogging through Bowser's Castle toward the end, Mario reaches six doors, leading to instances of three kinds of challenges. Two are straight combat, two are platforming action, and two are a gauntlet of dime-store brain teasers, hosted by a green Hammer Brother named "Dr. Topper". On the menu: peg-jumping puzzles, counting games, trivia quizzes about the RPG itself, and an infuriating "Who finished what place in a triathlon?" word problem. You only have to pass four of six doors, but randomly speaking, you'll have to face at least one of them.
 * Used a little easier early on, in the Sunken Ship. A series of platforming challenges give nautically themed clues to a six-letter word puzzle to enter the Boss Room. None of the challenges have to be completed, if a player can suss out a fitting word from the given letters. Both the quiz-gauntlet and the word puzzle are relatively simple affairs, but for people in the game's intended age range, they could be pretty stymieing, as they relied on critical thinking and some outside information.
 * Final Fantasy VI had a very interesting minigame built into the plot, wherein the team has to sit down for dinner with Emperor Ghestal and make small-talk. Several questions are asked of the player, for toasts and such, most of which offer three possible answers: sucking-up, magnanimous, and vindictive. He also answers questions about some plot-points, and then quizzes on which one was asked first. The game goes on through the dinner no matter what; since it's not possible to "lose", it's not exactly a critical puzzle, but "winning" nets the player lots of nice rewards. The puzzle is figuring out the right answers - each has a score attached to it, with the rewards based on the total earned. The answer isn't entirely obvious from the context, but the Emperor is trying really hard to apologize, so
 * Parodied in the PS1 game Shadow Madness; at one point, the heroes encounter a talking stone mouth located in a crypt that's been unoccupied for centuries. When it tells them to answer three questions in order to pass, one of the heroes asks why, to which it responds with, "You'd be bored too if you were me, honey."
 * Star Wars: Knights of the Old Republic:
 * Arithmetic puzzles get used for everything from decryption to demolitions.
 * The trivia questions both the ancient Rakatans and Darth Revan used to cover the tracks to their secret base.
 * Several puzzles in KOTOR are in fact classic puzzles given a more context appropriate reskin. The damaged extractor control system on the water planet is the same "measure 4 liters using only a 3 liter and a 5 liter container" seen in Die Hard 3, while the Sith tomb's energy ring transfer puzzle is really a jazzed up Towers of Hanoi.
 * In King's Quest VI, in order to get anywhere beyond a small beach on the Isle of the Sacred Mountain, you have to bypass a little obstacle aptly called the "Cliffs of Logic." Actually, that the Cliffs are an ancient test of intelligence is only the in-character explanation; out of character, the game practically demands you look up the solution in the guidebook that came with it.
 * Professor Layton is a game series that is made completely out of these things. Penny Arcade parody it here, suggesting it's a "Logic Opera": "every person you meet breaks into "puzzle" the way that Viking ladies tend to break into song, out of nowhere." The first game in the series, Professor Layton and the Curious Village, actually ends up deliberately invoking the trope:
 * Used to a ridiculous extent at the otherwise fantastically written Xenosaga series.
 * Shows up in the mad Finster's mind in Wasteland; you do have to get these right. Note that this guy's not exactly sane, and the fact that you're wandering in his brain with laser machine guns trying to kill him isn't helping his mental state much.
 * Pokémon:
 * Subverted in Diamond / Pearl. One gym presents you with three doors and a mathematical question - you go through the door associated with the correct answer. The thing is, the questions are so easy - and the main character is even given a calculator right at the start of the game - that the trainers who battle you behind the incorrect doors assume you deliberately got the answers wrong. One girl is pleased that you decided to battle her; another cheerfully agrees with your 'battle everyone' philosophy; and one boy complains 'why don't you just answer the questions properly?'. Then there's the last question: "What was the answer to the first question?" If you weren't really paying attention because the questions were so easy, you'll likely get it wrong.
 * And played straight in the rest of the games. Of note, the second-last gym of the first generation has a series of doors that can only be opened by answering a series of general-knowledge questions pertaining to the Pokemon world. Failure to answer correctly results in you having to fight the trainers guarding the doors - and since they give extra experience and cash anyway, why tax your brain?
 * It's subverted however, because the questions are for those who don't want to battle the trainers. You don't even need to answer the questions. Talk to the trainers to battle them and the door automatically opens if you win, whether you answered the question or not.
 * The SNES game Lufia 2: Rise of the Sinistrals does it a LOT. Like, every floor of every dungeon, cave, castle, tower or mansion is littered with puzzles of all sorts that you must complete to open doors.
 * It gets so extreme that one can reasonably argue that Lufia 2 is a puzzle game with a large story and RPG-elements in it.
 * In the Interactive Fiction game Gateway, you need to solve a puzzle to get to the first Heechee device. The puzzle ("which of these is not like the others") was put there so the species on the planet in question couldn't get at the device before they became smart enough. Hence, Only Smart People May Pass, which was its point.
 * Subverted in Disgaea 2: Cursed Memories, in which a minor boss in the Inevitable Tournament tries to challenge the heroes with the mother of all geo puzzles, causing the page quote from Tink in regards to Idiot Hero Adell. Adell takes one glance at the puzzle and states its correct solution without missing a beat, freaking out the puzzle creator and the rest of the heroes. Of course, to the player the real puzzle is getting to the solution that Adell pointed out. It's at the end of a maze of No Entry panels guarded by monsters. Although if you have enough range on your spells (which depends on how many times you've cast it before) you can hit it from the starting position.
 * In Medievil, the player can only gain entrance to the Asylum after answering a number of riddles "so perplexingly complex that no man has ever solved them" posed by Jack of the Green. Interestingly, the puzzles themselves are fairly easy to figure out, except for perhaps the last one. The real problem is in figuring out how you're meant to answer them.
 * More or less reversed in Amiga game The Chaos Engine [Soldiers of Fortune on consoles] which features fairly inventive puzzles which can only be interacted with by shooting them. In rooms full of enemies. Often, you'll have solved the puzzle without ever noticing it existed.
 * Used over and over again in Tales of Eternia, the first Tales game with the bright, involved, and unique sort of puzzles that also contributed to Tales of Symphonia being the hit it was. And then, without warning, subverted at the beginning of Volt's ruins: the Smart Guy Keele has been left behind, so while the rest of your party is busy scratching their heads and staring at the obtuse riddle on the front gate, Max walks up to the door and body-slams it down. The rest of the dungeon, of course, is full of puzzles, but damn if the scene wasn't hilarious.
 * In The World Ends With You, on the 4th day, you are boxed off by invisible walls and to open up these walls, you need to open up special boxes, which won't open unless you solve puzzles involving defeating specific Noise symbols. Additionally, to obtain the Secret Reports, you are required to get hidden items as part of your objectives, and are given cryptic hints as to where to find them, such as "Meet up with the secret" and "SHOWN A DREAM" . Also, some of the clues as to the daily objectives  are rather cryptic. Mind you, the characters manage to work them out, saving the player from the extra thought in those cases, at least.
 * The Myst series ran on this trope. The D'ni people in general were enamored of puzzle games, and Atrus picked up on it quickly when taken to the ruined city. Lampshaded in a parody of Revelation, by a frustrated Stranger working on the fireplace puzzle:

"A princess is as old as the prince will be when the princess is twice as old as the prince was when the princess' age was half the sum of their present age. Which of the following, then, could be true: the prince is 20 and the princess is 30, the prince is 40 and the princess is 30, the prince is 30 and the princess is 40, the prince is 30 and the princess is 20, or, they are both the same age?"
 * In Anachronox, to board the shuttle to Sunder (a Planet of Hats populated by scientists), the heroes must pass the Brain Bouncer, who demands explanations of complex scientific theories to ensure that the hopeful passenger really is a scientist of high caliber. This is then parodied when your helpful robotic buddy downloads the entire galactic scientific database into his memory, and you have to pretend to speak a language that the bouncer doesn't, so your robo-buddy can helpfully "translate" for you. Of course, there are two additional (humorous) swerves: the bouncer speaks all known languages (forcing you to "invent" a language), and at one point, after provided an answer that can be as short as three sounds and as long a twelve sounds, your robo-buddy prattles on for long enough that the scene fades out.
 * Resident Evil. At least in the 4th one, why does a scientific lab require you to manipulate chess pieces to open a locked door? No one knows. The novelization handwaves it by saying that Spencer, the man who designed the mansion, was insane and paranoid.
 * Portal. The puzzles at the beginning exist not to test the Portal Gun, but to see whether Chell is smart enough to use it.
 * Silent Hill has a lot of this, but Silent Hill 3 stretches it into true absurdity with a puzzle requiring an astoundingly thorough knowledge of the works of Shakespeare to pass (on Hard mode). Of course, it's Silent Hill we're talking about here - making sense is purely optional and any puzzle that can be explained with sufficiently elaborate Epileptic Trees (like, say, a 20 page forum debate between fans who have memorized the game) is obviously logically sound by the laws of the place.
 * Face it, the Zelda series is built off this trope. Forget fighting monsters, the meat of the dungeons is pushing around blocks in a grand scaled puzzle box to get to the MacGuffin. In The Legend of Zelda Twilight Princess, there is a point where Wolf Link, trying to enter the sacred grove that houses the Master Sword, is confronted by two malevolent-seeming statues. The statues explain that if he can get them back onto the spots where they're supposed to be standing, he can enter. Since the one of the statues will mimic his movements and the other will do the opposite, he has to jump around in the correct sequence to get them to shift onto the indicated squares and thus open the door.
 * Or how about that sliding box puzzle in Snowpeak? Mm-hm.
 * The Kingdom of Loathing does this with the Altar of Literacy that people have to pass to gain access to the chat. Its trials include typing a sentence and answering the "unspeakably difficult" trivia question "What colour was George Washington's favorite white horse?" Even though it's meant to be a comical RPG in general, it is an unspeakably good idea.
 * Possibly Trauma Center: New Blood, where to
 * In Valkyrie Profile there is an Egyptian-themed pyramid dungeon, in which the Sphinx presents the famous riddle to Lady Valkyrie. Her reply is simply "..." and she is allowed to pass.
 * This is the central premise behind the gameplay of Another Code: For some unfathomable reason, the designers of the mansion on Blood Edward Island thought that it would be more efficient to use logic puzzles instead of keys or handles. The most prominent example I can think of is the riddle square you need to open to get out the medallion.
 * Brain Lord is Exactly What It Says on the Tin, and EVERY that doesn't involved 'kill all enemies in the room' will genuinely test your reasoning ability....or patience, if you go for trial and error.
 * In the game Brothers Pilots, a fridge is locked by a puzzle. After you open it, a cat comes out and opens the door your characters were unable to open by simply pushing it (your characters try to pull it). Apparently, solving this puzzle was simpler than opening an unlocked door.
 * In the fourth Ace Attorney game, Apollo has to figure out how a professional magician pulled off one of his illusions. Not for any relevant reason, but because The Judge has decided that he wants to know how it was done, and that he wants Apollo to explain it to him. Once he understands, they continue with the actual trial.
 * Subverted in Planescape: Torment: the night hag Ravel Puzzlewell asks everyone who seeks her out the sphinx-like question, "What can change the nature of a man?", then tortures and kills everyone who gives the wrong answer.
 * The game also provides the answer.
 * No, it's
 * Actually, the Nameless One's "best ending" has him stating that
 * Baldur's Gate II has several such moments. The oddest riddle is one that makes sense as game dialogue but would be quite horrible if someone actually came to you and spoke it like this:

""Maker's Breath, Andraste only favored the clever it seems.""
 * In Exile 2, to address the Vahnatai Council you must complete two out of three tests: the Test of Strength (a series of combats), the Test of Speed (outrunning a wall of quickfire), and the Test of Mind (word games, math puzzles, riddles, and a maze). You might suspect that most players would skip the latter. In the remake, Avernum 2, the Test of Mind was replaced with the Test of Patience (a Block Puzzle).
 * Banjo-Kazooie's final level is a board game. It practically lampshades this trope, asking questions about various events in the game as well as matching sound effects and jingles to what they mean.
 * At one point in Dragon Age, the character must complete a relatively easy puzzle using party members to stand on plates to create a bridge to reach the ashes of the prophet Andraste. If Alistair is in your party, he'll comment on this:


 * Leliana also jokes about how you may have to "all join hands and sing a happy song to get across."
 * That quest also has a room full of people who give you riddles and attack you if you answer incorrectly.
 * Star Trek: The Next Generation: ”A Final Unity: The room guarding the Fifth Scroll.
 * Killer7 has a number of strange puzzles in bizarre and unlikely places. Of course, considering the game we're talking about, words like "strange" and "bizarre" are highly relative...
 * In both Paper Mario and its sequel, there are puzzles where you're required to answer questions about the game to proceed (or at least, to avoid a tricky boss fight).
 * Castle of Dr. Brain is built on this, with plenty of puzzles, labyrinths and other challenges. However, the doctor isn't trying to keep you out, just test you to see if you're good enough to become his assistant.
 * Likewise, Quest for Glory IV has Dr. Cranium (supposedly an ancestor of Dr. Brain), whose lab is behind four different puzzles, though all but one are interconnected. Unlike his descendant though, Cranium just wants his privacy and is sufficiently impressed when you enter.
 * The dwarf logic puzzles in Darklands are built on this. (With one exception, which due to writer error is a Guide Dang It.)
 * In Guild Wars:Nightfall, the Dasha Vestibule mission has a room with six pedestals with composite numbers and four with primes. The player must chose two composite numbers such that all four primes are factors of one of the chosen numbers.
 * Used as a joke in the "Elusive Golemancer" mission in Guild Wars: Eye of the North. "We designed the traps to keep less intelligent creatures out. We Asura have no problems with them. You, um, you should be fine. Yeah. You'll be just fine."
 * In Dead Space 2,
 * In Fallout games, this is character-based instead of player based, with Intelligence attribute checks, or various skill checks.
 * Drawn:The Painted Tower and its sequel Dark Flight are this in their entireties.
 * Shining the Holy Ark has a puzzle involving weights and scales before you can enter the dungeon proper. Also it has the infamous stone puzzle.

Web Comics
"Alt Text: Zelda, I dare you to make a game without this puzzle in it."
 * In Wapsi Square Monica meets Phix, keeper of the Bibliothiki, who asks her a riddle. When Monica answers, Phix gives her a prize. Later on Monica takes her friend Shelly to meet Phix, who asks her the same riddle [large-format strip]. The twist is that Shelly gives her a different answer but also gets a prize. Note that Phix doesn't actually say that either of the answers are right, she just says "good for you".
 * In Muse Academy, if you're in the dorm for science experts, the door asks newbies science questions, but it's to make sure they're at the right dorm.
 * Hilariously subverted in this Xkcd strip.
 * Also referenced here.
 * The Order of the Stick encounters the classic "one guard always lies, one guard always tells the truth" puzzle on the way to the Oracle of the Sunken Valley in this strip. Subverted when they pass it by shooting one of the guards in the foot; subverted again when Haley returns to the Sunken Valley.
 * Subverted with the Paradox Dragon strip of Partially Clips. This seems to be a popular trope to subvert in webcomics...
 * Subverted in these strips of The Adventures of Dr. McNinja. Turns out, it's  Or actually


 * Sluggy Freelance used it as well. One of the tests that must be passed to enter the Cave of Yffi (in "The Strombreaker Saga") is a "test of intelligence" that takes the form of a somewhat silly riddle. The heroes make it past by arguing their different answers were all as good as the "right" one. The gatekeeper then tries to make the riddle so specific that it can only be answered the one way ("a bat with lesions"). The villain nevertheless manages to answer it with "a nun with a spear through her head".
 * In a "Tempts Fate" segment in Goblins, Tempts runs across a sentient door asking him a riddle. An incorrect answer will spell certain doom. So Tempts just opens the door without answering and walks on through.

Real Life

 * High IQ Societies, like MENSA, require an IQ of at least 130 to join. However, it's become evident in recent years that IQ testing may not be a very accurate way to gauge intelligence.
 * Some scientists think that intelligence may be immeasurable and that an intelligent person can be identified simply by a few defining characteristics, like the ability to think abstractly and learn from experience. To their credit, though, there are some pretty smart people in those societies.
 * This is the point of the technical interview for information technology jobs. The interviewers will give you programming-related logic puzzles to solve and they consider how you attempt to solve these relatively basic problems to assess how well you might handle more complex coding work.
 * Extremely difficult subjects are this. Being stupid pretty much makes trying to get into Medical School a waste of time.
 * Graduate school oral exams (and, to a lesser extent, the dissertation defense) are pretty much this, since the committee can, theoretically, ask you anything related to the subject in question.