Tricking the Shapeshifter

"You know the trick. The clever mortal convinces the stupid djinni to squeeze inside a bottle (or some other confined space) then stoppers him up and refuses to let him out unless he grants three wishes, etc., etc. Ho hum."

- Bartimaeus, The Golem's Eye

A.K.A. Bet You Can't Make Yourself Really Small... (a.k.a. Bet You Can't Fit In This Bottle, a.k.a. Let's See You Turn Into A Mouse...)

When two shapeshifters square off, they have a Shapeshifter Showdown. But what happens if an evil shapeshifter or Reality Warper faces off against a mere mortal?

Easy: the mortal just needs to trick the villain into turning into something he can defeat, or to enter a container in which it can be trapped! This is usually done by appealing to the shapeshifter's ego, either through flattery or through dismissive skepticism:

"Wow! What an impressive lion you are - I bet you make a gorgeous cat! Ooh... what about a mouse? Can you do that?"

or

"Pshaw! You expect me to believe that a djinni your size came out of that tiny bottle? Ha! I'll believe it when I see it!"

This could be how the Evil got Sealed in the Can. Lately, some shapeshifters have started becoming Genre Savvy about this ("Did you honestly think I would fall for that old chestnut?"), but it is still played straight as often as it is subverted.

Anime and Manga

 * According to a Super Mario Bros. anime, Bowser's a bit too smart to fall for this.
 * Back in Dragon Ball when Piccolo was still a bad guy and faced off against Goku, he at one point made himself grow much larger. Goku, somewhat impressed, remarked that if only Piccolo could become even bigger he might be in trouble. Piccolo promptly did so... and Goku flew down his throat to retrieve the Sealed Good in A Can that he had previously swallowed. Thanks, Piccolo.

Comic Books

 * Shows up in The Sandman, with Lampshade Hanging, during the sequence where Lyta is hallucinating and/or shifting between seeing the real world and the Dreaming.
 * In a Mighty Mouse comic book, there's a story called "The Bad Genie". The titular genie, a cat of course, is a Card Carrying Villain who forces the mouse who freed him to serve him, and also pushes aside some houses so he can stretch out. After brute force, Mighty Mouse tries the "bet you can't fit in your lamp again" gambit, but he's too tired to argue...
 * In an issue of JLA, Batman uses this tactic against the all-powerful Metron. Metron prides himself on his knowledge and has never been a human, so Batman convinces him to take on a flesh and blood form to see what it's like. Then Batman beats him in one punch.
 * This is one of the few ways to defeat the Absorbing Man, who can duplicate most superhuman powers and just about any material substance (though he nearly always needs physical contact)--get him to turn into something inconvenient or that is more than his powers can handle.
 * In his first appearance, The Mighty Thor made him touch helium, so he turned into helium and floated helplessly into space, though that raises the question of why he doesn't turn into the oxygen, nitrogen, and CO2 in the air already.
 * This can lead to Hoist By His Own Petard when the Absorbing Man overestimates what he can handle. One fight with the Incredible Hulk led to him trying to absorb the power of the very Earth itself, only to explode when the Earth's power proved too much for him to absorb. He recovered. Eventually.
 * Wonder Woman goaded The Queen Of Fables into turning into a dragon, then quickly buried axes into her eyes.

Fairy Tales

 * Puss-in-Boots tricks a shape-shifting ogre into becoming a mouse, then eats him.
 * The original version of The Sorcerer's Apprentice has the apprentice tricking the evil master into turning into a drop of water, which then falls into a river.
 * There was also a story where the shapeshifter turned into a fish (swimming in a river) as part of a chain of transformations to show the normal hero his power. The shapeshifter says he'll change from the fish into a mountain, but the hero says he'd be more impressed if the shapeshifter could change into a drop of water. He does, and washes away with the river.
 * Wiley and the Hairy Man has the titular Wiley do this to the shapeshifting Hairy Man as one of the three tricks he has to pull.

Film-Animated

 * Sort of used in Aladdin, where Aladdin does this to Genie to get them out of the cave. Though Genie does not do any shapeshifting, he does take the Schmuck Bait out of sheer ego. Later, the titular hero tricks Jafar into turning into a genie, which immediately causes him to be sucked into a lamp. However, Jafar does need Genie to do this, so he couldn't do it all on his own. It did, however, use up Jafar's final wish and prevent him from using his powers (which the Genie had already made quite vast with a previous wish) against Aladdin.

Film-Live Action

 * In Fantagiro the heroine tricks the Black Witch into transforming into a crystal - which she shatters.

Literature

 * "The Fisherman and the Djinni" from The Thousand-and-one Nights (better known as Arabian Nights): The fisherman feigns skepticism to trick the djinni into returning to its bottle, which he promptly stoppers. Possibly the Ur-example of this trope.
 * Referred to (and subverted) in Starik Hottabytch (Old Man Hottabytch) by Lazar Lagin. A Jackass Genie almost falls for the trick, but at the last moment remembers that "a thousand one hundred and forty-two years ago a fisherman fooled me in just the same manner.".
 * Puss in Boots tricks the ogre into turning into a mouse, which Puss eats.
 * This is presumably why Puss has the reputation of being a "Notorious Ogre Slayer" in the Shrek series. However, neither Shrek nor Fiona has shown any signs of being magical. While we don't know about other Ogres yet, it'll be interesting to see how the writers deal with this in Puss In Boot's long-teased origin story film.
 * Similar thing happened in a story of Brazilian Big Eater Magali: she tricked a shapeshifting villain into turning into a roasted chicken with potatoes...
 * In Mercedes Lackey's retelling of Puss in Boots, Reserved for the Cat, Thomas attempts to trick a troll into doing this. Unlike the ogre in the original however the troll is not an idiot, and shifts again to catch the cat by the throat when he pounces.
 * In response to an ominous prophecy, Zeus tricks his pregnant lover Metis into turning into a gnat, which he then inhales. (An oracle had foretold that if Metis gave birth to a son, that son would overthrow his father. Turns out it's a girl. As a result, the goddess Athena is born from Zeus's head.) This variation of the myth is fairly late, but still Older Than Feudalism.
 * The Bartimaeus Trilogy: When Kitty tries to pull this on Bartimaeus, he scoffs at the idea that he would be dumb enough to fall for one of The Oldest Tricks in The Book. He notes, however, that had it worked this would be a very powerful binding charm since he would have entered of his own free will.
 * It's implied that it's happened to him at least once in one of his footnotes in Ptolemy's Gate. Which would explain why he would know why the charm would be so powerful.
 * The Goosebumps book "Attack Of The Mutant" had a shape-shifting villain from a comic book actually be real. Early on, we're told that if the villain turns into liquid, he can't change back. A kid claimed to be a superhero who could only be killed by acid, so the villain turns into acid, and thus is another Chekhov's Gun fired.
 * This is one fundamental strategy for dealing with a boggart in Harry Potter.
 * It's also how is defeated in Animorphs, though it took a little more than simply taunting him.
 * Used rather cleverly by Jon-Tom to  in the Spellsinger novel The Moment of the Magician.
 * Although not intentional, Mulgarith the ogre in The Spiderwick Chronicles is defeated when he turns into a bird to get away and ends up.
 * While not a shapeshifter itself, Com-Pewter had the power to summon anything to serve it. The heroes escape its chamber by verbally expressing fear that it will summon.

Live Action TV

 * Lampshaded in Star Trek Deep Space Nine. A little girl tells the real shapechanger Odo a old fairy story about a hero named the Great Minra who tricked an evil changeling into turning himself into a loaf of bread. To her surprise Odo gets to the end first ("The Great Minra gobbled him up"), and when she asks how he knew Odo wearily points out that the fictional changeling wasn't very smart.
 * And when the girl asks Odo to turn a loaf of bread, he asks; "Why? So you can gobble me up? I don't think so."
 * Further subverted in one novel to series where Odo warns off a Cardassian with a tale about how he voluntarily transformed himself into some food the certain alien liked, allowed himself to be eaten, and then expanded in the alien's stomach, ripping him apart. (It's implied that Odo's lying about having actually done that, but the fact that he could do that is terrifying enough).
 * In the 2010 Doctor Who episode "The Eleventh Hour",
 * Specifically, it's taking the form of
 * Wembley gets rid of the Mean Genie this way on Fraggle Rock.

Religion and Mythology

 * In Greek mythology, Zeus realized that he had to get his wife, Metis (goddess of prudence and magical cunning) out of the way, since it had been prophesied that she would bear powerful children, and he feared being assassinated. He suggested that they play a "game" of changing shapes, and, when she turned into a fly, he swallowed her whole. She was a pretty good sport about the whole thing, and from thereafter she lived inside his head, giving him good advice. She also gave birth to their daughter, Athena, who had to be delivered via skull.

Video Games

 * Kecleon the Pokémon changes type depending on what attack is used on it. You can use an attack, then one of a type that is strong against the previous attack For Massive Damage.
 * The Pokémon anime actually averted this with the Orange Islands match against Drake. His first Pokemon is Ditto, and when Ash is suggested to switch out Pikachu he says Ditto would just transform into the next one sent out.
 * Note that this is completely different from the games. When Ditto turns into one of your Pokemon, it stays that way throughout the battle, so you can switch to a Mon that's strong against what it transformed into.
 * Actually, for the Kecleon example you don't even have to use more than one type. Ghost and Dragon are both strong against their own type, though with Ghost you have to use another attack first since Kecleon starts as a Normal-type, which is immune to Ghost attacks. Porygon's Conversion move works similarly, though Conversion2 (which turns into a type strong against the one used) is much more difficult to exploit since there's the element of chance involved. Of course, in both cases Porygon doesn't even have to use either move, but you know, just in case...
 * The same tactics are used to trick a verbal shapeshifter in KotoR, enabling you to use his voice mimicry to break a voice lock.
 * Whether said shapeshifter is tricked or just doesn't care is up to discussion. Paraphrasing : "... the morality chip most droid are believed to possess forbids me from mimicking a human voice."
 * The final battle in King's Quest V has the hero engage in a shapeshifting duel with an evil wizard. After his first three forms are countered, the wizard gets mad and transforms into a raging fire... which is when that raincloud spell you just learned comes in real handy.

Webcomics

 * The "Contains One Space Battle" story in the webcomic Goats has Jon and Phillip meeting God after Phillip argues he doesn't exist. God appears as a pirate named Larry, and explains he can take many forms, such as a slightly taller pirate named Sebastian. The guys are unimpressed, and God tells them to pick a form. Phillip suggests a pork chop. God becomes a pork chop, then Phillip eats him, thus winning the argument. This is, incidentally, the pivotal event behind the later plot-driven era of the comic.
 * In Captain SNES, Alex comes up with a (fake) plan to get rid of the personification of his hatred, which resembles Zeromus. He will get really angry, causing "Zeromus" to grow so big that he'll explode. Alex points out that the only way Zeromus can counteract this plan is if he can deliberately shrink himself. Zeromus demonstrates that he can deliberately shrink himself... by shrinking himself to be just small enough to fit into Alex's unbreakable jar.
 * Parodied in Van Von Hunter when the title character faces a vampire that can switch between human and monstrous form. "A beautiful woman is so much more intimidating than a vampire." Two panels later, "They are easier to stake, though."

Western Animation

 * In the same vein, Danny Phantom tricked a Reality Warper human to become a ghost so Danny could trap it in his Fenton thermos.
 * Alluded to in the "Mickey and the Beanstalk" sequence in Fun and Fancy Free. Unfortunately, Willie the Giant might be a little more Dangerously Genre Savvy than he looks. And it's sooo much better to turn into a pinky bunny then a gnat.
 * Ben 10 Alien Force: Vilgax finally succeeds in stealing the Omnitrix but can't get it to work for him. Ben volunteers to show him if he releases his friends. Ben uses this opportuntiy to set the Omnitrix to turn Vilgax into Goop, a giant amorphous blob of gel, and steals the anti-gravity device the alien needs to maintain its shape, reducing Vilgax to a puddle.
 * In The Avengers: Earth's Mightiest Heroes, the Absorbing Man touches Thor's hammer Mjolnir and converts himself into metal that can harm a god. Thor, however, points out that he can control Mjolnir, and can therefore control Absorbing Man, whom he uses as a human-sized hammer for the rest of the fight.
 * Used straight in an episode of Aladdin the animated series. Genie needs to stop a caravan from proceeding. Aladdin who is at that time a guardian of said caravan (long story) offers him to settle the matter by tossing a coin. Aladdin then makes it so that the coin falls into a lamp and the helpful simpleton Genie volunteers to retrieve it. It turns out that even a freed Genie cannot escape from a sealed lamp. Go figure.
 * In the Garfield and Friends retelling of Puss in Boots, Garfield manages to trick the ogre resident of a nearby castle into turning into to a roach, which he then squishes with his high-tops. It got better, unfortunately.
 * In Alfred J Kwak, this is played straight and subverted with the Evil Spirit of Darkness.
 * The spirit was defeated hundreds of years ago by a traveller who tricked him into going back into his bottle, and then sealed him shut.
 * When Alfred tries the same thing later on it almost works, but the spirit then remembers the details of how he was resealed again, and stops halfway through. Alfred only succeeds when he realizes that the Evil Spirit can be hurt by light, and forces him back in.