Then, this can mean they want to be rid of you, or exploit you, and there is the little matter of figuring out who would understand if you say it. Heaven help you if you accidentally learned it; you will find yourself knee-deep in trouble before you can blink.
In The Infiltration, it is a frequent point of failure — but if you do have the knowledge, it lets you in entirely. The Ancient Tradition, Ancient Conspiracy, and Ancient Order of Protectors take it very seriously.
Unlike Only Smart People May Pass, you can not figure this one out from the clues; you have to have learned it. (Occasionally, the Genius can manage to figure it out, but it will always take him serious time and effort, and it's not always possible even for him.) This is, if they did it right. Sometimes they were clumsy. Conversely, an Only Smart People May Pass riddle may turn into this if the answer is too insane or difficult.
- In the Original Sin tie-in for The Avengers, the heroes encounter a time traveler who claims to be an adult version of Franklin Richards, the young son of their friends from the Fantastic Four. He proves his identity to Black Widow by mentioning an anecdote from his childhood where she showed him how to make Improvised Weapons out of his toys.
- In Winter War, while meeting in an occupied city, Soi Fong and one of her Onmitsukidou use lines from a Tang Chinese poem as a password, switching off in the middle of lines and then skipping to the end. While someone sufficiently learned might know the poem, they probably wouldn't know when to switch off, or recognize what was going on based on the first phrase.
Kage: After battle...
Soi Fong: Many new ghosts cry. The solitary old man...
Kage: ...worries and grieves. (pause) To many places, communication is lost. I sit straight at my desk but cannot read my books for grief.
- In Tangled, the guard captain is tweaked with demands for a password during the rescue.
Shorty: What's the password?
Shorty: Nope! [closes hatch]
Captain: OPEN THIS DOOR!!!
Shorty: Not even close!
- In Frankenstein: The College Years, Doctor Lipzigger's computer security demands, in addition to a keycard he bequeathed to the protagonist duo, the answers to two questions: One about chemistry, the other about Star Trek. It was meant so that only the protagonists may unlock it, together.
- In Airheads, Chazz confronts Chris Moore, who claims he's a music executive, but Chazz thinks he's really a cop, so he asks him "Whose side did you take in the Van Halen/Roth split, Van Halen or Roth?" When Moore answers "Van Halen", he's immediately accused of being a cop, but he asks for another chance. So Chazz asks "Who would win a wrestling match, Lemmy or God?" Moore initially answers "Lemmy", but when Chazz imitates a buzzer, he changes his answer to "God", before Rex yells "Wrong, dickhead, trick question, Lemmy is God!", and Moore is forced out.
- In Back to the Future Part II, the old Biff Tannen of 2015 gains the trust of the young Biff of 1955 by starting his car in a way only he knows about.
- In Guards! Guards!, The Elucidated Brethren of the Ebon Night have a long string of passwords (as does every other secret society in the area, oddly enough at least some of them have the same ones, meaning they have to help each other's members to the right meeting place).
- Dune: Lady Jessica is able to gain acceptance among the Fremen by using phrases planted in their culture by the Missionaria Protectiva (which manipulates religious beliefs to benefit the Bene Gesserit).
- In Harry Potter, students in Hogwarts need a password to enter their dormitories. (With the exception of the students in Ravenclaw, who use a riddle — Only Smart People May Pass.)
- Doubly subverted in Septimus Heap, since while the DoorKeeper of the House of Foryx doesn't allow Jenna and Beetle to enter even after they have resolved the puzzle that is The Right of The Riddle, they eventually get into the house with violence.
- The Kaiel Death Rite, in Courtship Rite, which is applied to heretics, consists of seven increasingly difficult deadly tests. Each test must be designed so that someone who is familiar with "the common wisdom" can pass, because it is the common wisdom that is threatened by heresy. When the protagonists are ordered to marry Oelita, the Gentle Heretic, they decide to use the Death Rite to test her fitness to wed them.
- In Rick Riordan's The Heroes of Olympus novel The Mark Of Athena, the ghosts of Mithritic initiates think they have this. Annabeth does indeed have some of their secret knowledge, but bluffs through the rest, notably added by her ability to make guesses based on the room's decor.
- In Dan Abnett's Ravenor vs. Eisenhorn novel Pariah, Lupan tries to make a veiled approach to Beta. Unfortunately for him, the code terms he used were so ineptly woven in as to signal that something was wrong to her.
- Inverted in Illuminatus!. Robert Drake spends a considerable amount of time and effort trying to force his way into The Illuminati by demonstrating his knowledge of the Ancient Conspiracy.
- In a short story note , the villain steals art carvings and tries to sell them as his own work. The original sculptor takes him to court, where a judge orders them each to carve an image as he watches. The plagiarist's work is obviously much worse, so he is found out.
- In Doctor Who, when the Doctor meets up with the amnesiac Brigadier, teaching at a boys' school, the Brigadier's attitude undergoes an abrupt change when the Doctor mentions UNIT — he still doesn't know him, but anyone with sufficient secret clearance to mention it ought to know better than to talk like that.
- On No Ordinary Family JJ proves he belongs in the Smart People's Club by citing its latitude & longitudinal coordinates.
- Pops up repeatedly in the last two seasons of Stargate SG-1. In order to access the ancient treasure in "Avalon", one must possess "wealth of knowledge and truth of spirit." Similarly, "wisdom" is one of the virtues required to find the Sangraal in the season 10 two-parter "The Quest." In both cases, the protagonists are required to not only solve puzzles and riddles, but also have prior knowledge of Ancient language and culture (and the King Arthur mythos.)
- The Magicians: Only humans from Earth can become the kings and queens of Fillory, so the Knight of Crowns has to test aspirants to be sure they're telling the truth. He does so using bizarre pop culture questions from the 90's ("Is it not the 90's on Earth?"). Eliot ultimately wins the crown of High King by reciting Patrick Swayze's speech from Dirty Dancing.
Knight: What was the hit song made by the children of famous actors?
Margo: ...dude. That's hella vague.
- Betrayal At Krondor has a great many chests called "Wordlocks" that are essentially combination locks with letters instead of numbers, and they have riddles on them. The answer to the riddle is the combination, so most of these follow a different trope, though one special chest for a sidequest contains a lore-relevant riddle that requires you to learn the answer before you can open it.
- In Impure Blood, Dara uses it twice:
- In Girl Genius, Violetta inverts it, thinking that Moloch's ability to get into the rafters shows he must have been trained or have some secret knowledge. He assures her that he knows he doesn't want to get munched on by the thing below them.
- In Erstwhile, the prince questions the bride about things during the ceremony and says if she doesn't know them, she's not his true bride.
- In Rusty and Co., the bottle fairy has forgotten her Riddle Me This, and replaces with a riddle that no one would know.
- In Grrl Power, Syndey puts Leon to the test before verifying that he is indeed a proper nerd.
- In the Futurama episode "Fear of of Bot Planet", two characters in disguise must prove they are robots by passing such a test:
Robot #1: Administer the test.Robot #2: Which of the following would you most prefer? A: a puppy, B: a pretty flower from your sweety, or C: a large properly formatted data file?Robot #1: Choose! (Leela and Fry whisper)Fry: Uh, is the puppy mechanical in any way?Robot #2: No! It is the bad kind of puppy.Leela: Then we'll go with that data file!Robot #2: Correct.Robot #1: The flower would also have been acceptable.Robot #2: You may pass.
- In medieval times, masons needed a way to know whether other masons really knew their stuff, since they traveled a long way on jobs, failures of skill could be disastrous, and it was really hard to check with those who taught them. Their solution was secret rituals — only a skillful mason would be taught them, so knowledge proved his skill. (The true origin of the Freemasons.)
- To anyone who has ever forgotten a code or password to access an account, this trope applies. Painfully.
- This Cracked article describes how easy it is if you know enough about someone, to infiltrate their email and facebook accounts by guessing their security questions.
- Inverted in some cases—someone who knows too much can appear to have researched a topic artificially out of Genre Savvyness, as one German spy in the US discovered when he could complete a line from the third stanza of the US anthem.