"You just lost The Game!"
This is about a phenomenon of your very thought process: telling someone not to think about something will inevitably and involuntarily lead to them thinking about it. Telling yourself not to think about something may be even more futile, as by thinking about not thinking about it, you are thinking about it.
(And now, not only are you thinking about it, but you have a headache.)
The suggestion that you should not be thinking about something is, in itself, sufficient to induce thinking about that thing. No other provocation is required—you don't have to be surrounded by elephants for the old schtick to work. For instances when people can't stop thinking about some aspect of a person because it is so very noticeable, even if they don't want to mention it due to politeness, see Ignore The Disability. When thinking about a particular action makes it more difficult than performing the action unthinkingly, you are faced with the Centipede's Dilemma. Telling someone not to do something in hopes that they will decide to go and do it is plain ol' Reverse Psychology, or one of its Sub Tropes.
If you live in a universe with Thought Crime, or one where Your Mind Makes It Real, this sort of thing can be particularly dangerous.
This phenomenon is actually a direct result of how the human brain is wired. Neurons that are used to interpret words like "elephant" have synaptic connections to the neurons used to picture and think about the concepts those words represent; if they weren't, verbal language itself probably couldn't function.
See also Forbidden Fruit, Don't Look Down, Streisand Effect and Suspiciously Specific Denial.
Buck Godot: Zap Gun for Hire has one at the end of a story where the Prime Mover tells a reporter that if she even thinks about the events that just happened (which would reignite the war they just barely prevented), her head will explode. She nervously jokes that he can't be serious; he suggests a lobotomy.
Ghostbusters. The gang is on the roof facing off with Gozer, she tells them to choose her form, Venkman figures it out and tells the rest of the group to keep their minds a blank. Cue Stantz thinking about the Stay Puft Marshmallow Man. Gozer then becomes a giant Stay Puft Marshmallow Man and terrorizes the city.
In The Good Witch's Garden, a little girl is cured of nightmares by being told that she must not, under any circumstances, dream about bunnies. Three guesses what she dreams about, and the first two don't count.
A guy has an impotence problem. One day, late at night, He's sitting in a bar, very drunk and complains about his problem. Then some sleazy guy appears and tells him: "I have some special medicine for you! It costs 1000 bucks, but it'll cure you forever! Just swallow it and wait for five minutes - but remember one thing: You mustn't think of a rhinoceros during that time, or it won't work!" Guess how it turns out.
Subverted in one of the novels featuring Tiffany Aching, where Granny Weatherwax proudly proclaims that she is "perfectly capable" of not thinking about a pink rhinoceros. Tiffany eventually twigs that this is because Granny doesn't know what a rhinoceros is.
In the novel Sourcery, travelling inside a magic lamp being held by one of the people travelling, which is moving to its destination because the person holding it is, is possible as long as nobody thinks about the fact it really isn't. One of the characters compares it to "not thinking about purple rhinoceroses".
In The Light Fantastic, Rincewind and Twoflower hitch a ride on a huge rock which a young druid is flying to an under-construction stone circle. Informed that the rock stays up because the druids have persuaded it to fly, and will fall if anyone's thoughts remind it that rocks can't do that, Rincewind struggles to think of rocks swooping and soaring around rather than sitting on the ground. He's miserably aware that he's not very good at it.
There is a Russian book called The Tale of Hodja Nasreddin (the lejendary Nasreddin is a mullah, but here he is described as a mischievous vagabond). In one chapter, he tells the usurer Jafar that he is a powerful (and expensive) healer, but his healing won't work if Jafar or anyone in his family thinks of the red monkey (and he describes it in excruciating detail). His clan spent much of the following night arguing about who was the first to think the forbidden thought.
In The Dresden Files novel Ghost Story, Harry's ghost is told that he can avoid sinking through any surface he "sits" on by not thinking about it too much. Which causes him to immediately fall through the bottom of the car. He does get better at not-thinking later on.
Near the beginning of the Lensman novel Gray Lensman, this is used to show how well-disciplined Kinnison's mind is — he is able to not think about something he saw in Helmuth's base until he's back on board the flagship. (It was a thought-triggered bomb, so if he hadn't had that mental discipline it would have ended the series early.)
In The Eyre Affair Thursday's time travellng father shows up and tells her to tell her mother not to paint the bedroom mauve, because she does so in the future and he hates it. Thursday dutifully tells her mother, only to discover that her mother had no plans to paint it at all, let alone mauve; but after Thursday tells her not to she does.
In The Hitchhiker's Guide to the Galaxy, the secret of flight is "throwing yourself at the ground and missing"—in other words, you have to fall and then completely forget about the fact that you're falling before you hit the ground. Then, of course, you can only keep flying as long as you keep forgetting that you should be falling. The books note how difficult this is to pull off in practice. The first time Arthur Dent flies, he's only airborne for less than a minute.
Live Action Television
My Name Is Earl. While Earl is in prison he takes a creative writing class, but can't think of anything to write about. His cellmate Sonny is taking the same class and tells him about his story, which involves beating up a gymnast. Earl tries to go into his imagination, but it's a White Void Room with nothing in it but him...and a gymnast. The gymnast offers to be in his story, but Earl declines because "that's Sonny's thing." Earl then spends the next 4 1/2 hours in the room, and the only thing he sees is the gymnast from Sonny's story.
The Mentalist. Jane will often tell a suspect something like "Don't think about where you put the gun" and then watch where the suspect's eyes go, which tells him where the gun is. Although likely as not it'll be a misdirection, telling Alice this while Bob (the real killer) is in the room, so Bob will look while he thinks Jane is paying attention to Alice.
Also invoked in Coupling as the basis to Jeff's "Giggle Loop":
Jeff: Basically, it's like a feedback loop. You're somewhere quiet. There's people. It's a, it's a solemn occasion. A wedding. No, i—it's a minute's silence for someone who's died. Minute's silence, ticking away. *tick, tock, tick, tock* The giggle loop begins. Suddenly, out of nowhere this thought comes into your head: "The worst thing I could possibly do during a minute's silence... is laugh. And as soon as you think that you almost DO laugh. Automatic reaction! But you don't, you control yourself, you're fine. *exhales* ...but then you think about how terrible it would've been if you had laughed out loud in the middle of a minute's silence. And so you nearly do it again, only this time, it's a BIGGER laugh. And then you think how AWFUL this BIGGER laugh would've been, and so you NEARLY laugh again, only this time it's a VERY big laugh. It's an ENORMOUS laugh. Let THIS bastard out, and you get whiplash! And suddenly, you're in the middle of this completely silent room, and your shoulders are going like you're drilling the road! And what do you think of this situation? Oh, dear Christ, you think it's FUNNY!
In the Cyberax arc of Bugs, one of the good guys asks Ros not to think about elephants, to bait her away from Cyberax's tought-activated mental bomb.
In Babylon 5, Trakis is "warned" not to think about irrelevant facts such as Adira Tyree's current whereabouts while attending a telepath-monitored negotiation. Of course, that information then appears in Trakis' surface thoughts, where Talia can perceive it without deliberately probing (that being the limit of how far she was willing to bend PsiCorps rules).
Fawlty Towers: In "The Germans" episode Basil tells himself (and others) to not mention the the war. He fails miserably, to the point of making one of them cry, after that he does a Silly Walk Hitler impression.
Basil Fawlty:Polly, is these German too?
Polly:oh yes, but I cou
Basil Fawlty:Right! Right! Here's the plan, I'll stand there and ask them if they want something to drink before the war...Before their lunch! Before their lunch! Do not mention the war!
Basil Fawlty: Ah, wonderful! WUNDERBAR! Ahh! Please allow me to introduce myself, I am the owner of Fawlty Towers. And may I welcome your war... your war... you wall... you all... you all, and hope that your stay will be a happy one. Now, would you like to eat first, or would you like a drink before the war... AHH! Er... trespassers will be tied up with piano wire... SORRY, SORRY!
Misfits: Nathan has trouble hiding his attraction to Kelly from her Mind Reading powers.
Nathan's Inner Thoughts: Don't think about shagging her. Don't think about shagging her. You're thinking about shagging her. You're an idiot.
In one The Far Side strip, a man visiting a hospital patient in a plaster cast says, "You're not itching anywhere are you? Because you can't scratch you know. Don't even think about itching, it'll drive you nuts".
In Portal 2, Cave Johnson describes some sort of reaction that would cause the frontal lobe of your brain to become vitrified. Of course, he points out that picturing the reaction causes it, so don't think about it.
In Freefall, Sam gets the robots to think up a devious master plan for him this way:
Sawtooth: All we have to do is not think of a devious master plan for Sam.
Dvorak: You didn't.
Qwerty: Oh, come on! It's like being told not to think of a rhinoceros with a teacup.
Commander Badass: Yeah, time travel's been super stable ever since scientists figured out that th' less ya think about it th' more solid and seamless everything hooks up. S'like they say, "A watched cheetah never bevels."
Jones: That is not a thing people say. What does that even mean? Literally no person has ever said that befo—
[Suddenly, they're both in the future.]
Commander: 'S way more efficient than saying "Don't think about time travel."
"The Game". note This is an internet fad that uses this trope as its very core: You lost The Game when you think about it. So it's popular to see someone in the internet saying "you lost The Game" or just "The Game" to make someone lose.
Happens in a first season episode of Men In Black The Animated Series. K had been infiltrating an psychic alien conspiracy trying to invade earth for years by disguising himself as one of their own (who had willing let him do so because he had gone native). After explaining everything to J this happens:
K: Oh. And whatever you do, don't think about what I just told you.
J: That's the last thing you tell someone when you don't want them to think about something!
They are then immediately caught.
In one episode of Johnny Bravo, Johnny, inside of a dream, is on a date. After learning from the real world that anything he thinks of will happen in the dream world, his date randomly tells him to not think of her as a monster. Naturally, he has to then picture her as one, which turns her into one.
Five hats means that five tropers think it is ready to publish.
You are saying that you think this draft is ready to be published. That means the description is not ambiguous,
it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.
Is that what you meant to do?
You are saying this draft has a ready-to-publish hat it does not deserve and you are taking it back.