[[quoteright:89:http://static.tvtropes.org/pmwiki/pub/images/wind_up_key_82462_2332.jpg]]
One good way to show that something is a toy, toy-themed, or just mechanical is with a wind up key. Especially complements ToyTime, or alternatively, ClockPunk.

It can also serve as a WeaksauceWeakness if something needs to be wound up to keep functioning.
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!!Examples:

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[[folder:Advertising]]
* There's [[http://www.youtube.com/watch?v=wXuMld0VwuU a commercial]] for Pristiq anti-depression medicine which uses wind-up toys as a metaphor for how one feels when one is in the grips of depression, and when one is not.
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[[folder:Anime and Manga]]
* In ''Manga/RozenMaiden'', the living dolls come to life when someone winds them up using a key.
* [[RobotGirl Chachamaru]] in ''Manga/MahouSenseiNegima'' needs to be wound up every so often. It feels very good [[FantasticArousal to her]], so it often causes her embarrassment in the hands of an overenthusiastic winder.
* Ifurita in ''Anime/ElHazardTheMagnificentWorld'' qualifies, with all the expected sub-text (the keyhole is at the base of her spine). When fully wound, she uses the key as a magic wand with KillSat level of firepower.
* [[RidiculouslyHumanRobot Nano]], from ''{{Nichijou}}'', desperately wants hers removed so it won't be so blatantly obvious that she's... not exactly human. The [[ChildProdigy Professor]] who built her thinks it's cute.
** It does do something though. But this being the Professor it [[spoiler: just causes her big toe to shoot off like a rocket.]]
* In ''Tina the Wind Up Toy'', the titular character Tina and most of the toys that live on Wind Up island has to be wound up in order to function, and won't be able to move otherwise. There is one toy who doesn't have a key, though. (other than Tina's best friend)
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[[folder:Comic Books]]
* Flying Smurf's Aerosmurf from ''ComicBook/TheSmurfs'' story of the same name requires a wind-up key to keep its motor functioning. As he and Smurfette are being chased by Gargamel, the motor of the Aerosmurf gives out, and Flying has to use the key to get the motor running again before he and Smurfette crash-land.
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[[folder:Film - Animation]]
* A wind-up car appears in a quick gag on ''WesternAnimation/{{Robots}}''.
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[[folder:Film - Live Action]]
* ''Film/{{Hellboy}}'': Kroenen had to wind up his clockwork innards with a key.
* Truly Scrumptious pretends to be a "Doll on a Music Box" that has a large wind up key in ''Film/ChittyChittyBangBang''.
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[[folder:Literature]]
* Tik-tok in the ''{{Oz}}'' books. Interestingly, he has three keys that operate walking, talking and thinking for him.
* Played for creepy in ''Literature/VarjakPaw'', when the cat hero finds a bunch of very, very creepy cats... that turn out to be wind-up toys.
* The children's book ''Wagstaffe the Wind-up Boy'', about a boy who was converted into a clockwork {{cyborg}} by an oddball surgeon after being run over by a lorry. There's a brief scene where he looks at his reflection in a shop window, noting that the folded-down key is a barely-noticeable lump under his jacket.
* In the ''Literature/{{Discworld}}'' novel ''Discworld/ThiefOfTime'', the History Monk protagonists use an experimental device called a portable procrastinator to artificially increase the amount of time they can use. It's worn on the back and powered by manually winding up the key. This is absolutely vital for their continued movement once time breaks, [[spoiler:but only for one character]].
* For completeness, one should mention the clockwork mouse Mr Clicky, which the rats in ''Discworld/TheAmazingMauriceAndHisEducatedRodents'' often use to set off traps. They carry several with them in their travels, having agreed to discontinue use of Mr Squeaky since the sound of him being crushed was quite distressing to all.
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[[folder:Puppet Shows]]
* ''TheMuppetShow'' once had a robotic duplicate of Kermit the Frog, which had a wind-up key in its back.
* The titular castle in the classic Creator/{{Nickelodeon}} preschool series ''Eureeka's Castle'' has a giant wind-up key on the castle itself that the giant would wind occasionally; usually when a guest performer appeared.
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[[folder:Tabletop Games and Card Games]]
* ''TabletopGame/YuGiOh'' has [[http://yugioh.wikia.com/wiki/Wind-Up an entire archetype]] based on wind-up toys. Naturally, [[http://yugioh.wikia.com/wiki/Legendary_Wind-Up_Key the key]] is a spell card.
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[[folder:Video Games]]
* ''VideoGame/SuperMarioWorld'': The Mecha Koopa enemies have wind-up keys on their backs.
** Bob-ombs also have them, too.
* The first ''VideoGame/MarioParty'' had a "how many times can you wind up the toy in X seconds" minigame.
* In ''DonkeyKong64'', robot Kremlings called Krobots have these, and the theme tune itself even has a music box type wind up effect at the start, as seen [[http://www.youtube.com/watch?v=02UUBgoiwZw here]].
* ''VideoGame/LuigisMansion'' has the toy soldier bosses.
* The ''MarioVsDonkeyKong'' games feature wind-up Mini-Mario toys.
* ''MapleStory'': Various monsters in Ludibrium have them
* Lots and lots of these appear in the ''VideoGame/{{Syberia}}'' duology, seeing how it's literally crawling with [[ClockPunk all kinds of clockwork contraptions]]. Most notably, the train you are traveling on needs to be wound up on each station.
* The Clockwork from ''CityOfHeroes'', which are created from scrap metal, but almost always have one of these on their backs. The winders are also a common low-level [[ItemCrafting salvage]] drop.
* The Keymasters in ''DynamiteHeaddy''. Heather's mission is to collect all the keys to reveal the Dark Demon's castle.
* In ''EverQuest'', the Secrets of Faydwer expansion introduced the [[ClockPunk clockwork robots]] created by gnomes which all have a wind up key on their backs.
* Pokémon in ''PokemonRumble'' are all wind-up toys, so the key is used to wind them up before releasing them. One such key is even [[spoiler:the BigBad]].
* In ''VideoGame/AdventureQuest'', the Nightmare Queen's chess-themed minions are all sentient, life-sized toy soldiers, complete with wind-up keys in their backs. The PlayerCharacter can also purchase an identical-looking armor after completing the ''Frostval In July'' quest.
* Certain concept art for ''VideoGame/{{Skullgirls}}'' suggests that Robo-Fortune is powered by a wind-up key in her back.
* Clockwork keys are an item drop at Thugnderdome in ''VideoGame/KingdomOfLoathing''. They're significantly rarer than the other components of clockwork items; getting ten in a single run earns a trophy. They're also needed for the last stage of every clockwork item.
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[[folder: Visual Novels]]
* There are robots in ''DaCapo'' that are wound up by a key. They do have alternative energy sources, though.
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[[folder: Western Animation]]
* ''WesternAnimation/FeedTheKitty'': Marc Anthony takes a key off a toy car and pretends to wind up Pussyfoot with it to fool his owner into thinking that the cat is a toy. He succeeds, and Pussyfoot then gets himself into the aforementioned toy car, minus key. Marc Anthony finds it cute, until Pussyfoot manages to get the toy car working and starts driving erratically, possibly [[NiceJobBreakingItHero because of the aforementioned removal of the key]].
* Kilgore from ''WesternAnimation/MyLifeAsATeenageRobot'' is a pitiful toy robot, powered by a watch spring and a wind-up key, who dreams of destroying mankind.
* Mechanicles from Disney's ''WesternAnimation/AladdinTheSeries'' is often seen winding up his ClockPunk [[ClockworkCreature insect-like robots]]. He even has one dedicated to winding up all others, so he only has to wind up that one.
* In the WesternAnimation/DonaldDuck cartoon ''Donald's Diary'', Don's nightmare of being a henpecked husband culminates in a key growing on his back, making him into a robot doing chores for Daisy.
* WesternAnimation/YogiBear once put a key on his back and pretended to be a giant wind-up toy grabbing picnic baskets, after doing an experiment with Boo Boo. Yogi is stopped by a wind-up Ranger Smith.
* A common gag on ''Droopy'' cartoons is for his opponent to wind him up with a key to send him toddling away like a toy.
* In ''WesternAnimation/{{Wakfu}}'', BigBad Nox [[HorrorHunger must be fed every day]] with [[LifeEnergy wakfu]] through a giant key-shaped tube (which fits into a hole in his chest rather than his back, oddly enough.)
* In a ''WesternAnimation/DaveTheBarbarian'' episode, Candy is able to tell Dave apart from [[EvilKnockoff Mecha-Dave]] by pointing out the key on its back. Later, Mecha-Dave stops his battle with Dave to tell him to wind his key.
* At the end of the early 1980s ''Franchise/ScoobyDoo'' short "Scooby-Doo 2000", Scrappy-Doo had a fake wind-up key in his back.
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[[folder: Real Life]]
* At one point when the locomotive [[http://www.bluebell-railway.co.uk/bluebell/pics/BLUE_CIRCLE.HTML Blue Circle]] was based at the Bluebell Railway, it acquired a (fake) key.
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