->''Ngombi struggles to lift a huge styrofoam rock.''
-->-- Stage directions for ''Jungle Juice'', a play by Judith Prior.

AliceAndBob are on an epic adventure to find a treasure buried deep underground. They are making their way through a maze of tunnels, with only a flashlight and an ancient treasure map keeping them from getting lost. But oh no! The villain hot on their heels accidently sets off a bomb and the ground starts shaking under the heroes' feet! The ancient tunnels aren't built sturdily enough to take the tremors and the walls crumble around them!

Except the rocks that fall sort of...''bounce'' when they hit the ground...

When shooting in a studio, you can't just bring in a truckload of rocks and drop them on the actors. Even wood won't work - what if somebody is injured! The rocks could of course be done with CGI, but that would cost quite a deal, and be hard for the actors to properly portray.

What do we have left? Styrofoam!

This trope is a kind of SpecialEffectsFailure and is applicable in situations where light objects, such as Styrofoam, are meant to portray rocks, bricks or some other heavy material in a dramatic fashion, but fails to [[{{Pun}} lend any weight]] to the seriousness of the situation.
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!!Examples:

[[foldercontrol]]

[[folder: Fan Works ]]

* The boxes thrown between Bond and terrorists in ''WebVideo/DiamondsCut'' are obviously empty and wouldn’t hurt anyone, especially when both Bond and terrorists have guns.

[[/folder]]

[[folder: Film ]]

* In the commentary for ''Film/{{Underworld}}'', the movie's creators point out in a scene towards the end of the movie that some of the stone debris from someone getting thrown through a wall can be seen to float in a pool of water. Oops.
* ''Film/DragonballEvolution'': In the climax of the movie, the heroes are in a valley between rock pillars. Except the rocks look very light.
* In the climax of ''OurManFlint'', one of Flint's fleeing girlfriends is hit by a styrofoam "boulder" and it bounces right off.
* The opening to ''Film/{{UHF}}'' makes fun of this, as a rock bounces right off George Newman's head mid-fantasy and does nothing to him.
* The end of ''Film/{{Ghostbusters}}'' has debris falling from the top of a skyscraper, and in one shot you can see a rock, which had supposedly tumbled from several hundred feet in the air, fall straight down and bounce off of a ''wooden'' police barrier.
* Rocks in ''Film/MortalKombatAnnihilation'' tend to bounce a lot.
* Falling rocks at the end of ''The Terror'' start floating on the water.
* In ''Film/{{Congo}}'' rocks fell from the cave roof; some bounced and those that landed in the underground river floated.
* ''Film/TheThreeStooges'' used this a lot, to keep up the illusion that the three had the endurance of a typical cartoon character when being hit in the head with rocks or bricks.
* Seen occasionally in ''Film/TheLordOfTheRings'' films, as most of the sets were made of polystyrene (in fact, during production the films became the biggest consumer of polystyrene in the ''world''). Thus, any time there are earthfalls, the rocks will fall a little too lightly.
* A famous goof in ''Film/RaidersOfTheLostArk'' has Indy shove a loose cubical stone the size of a compact car hood out of a wall, and the shadow shows it bouncing several times as it hits the sand.
* During the climactic attack at the end of Disney's ''Film/SwissFamilyRobinson'' when the titular family rolls the logs down the hill at the pirates, one of the "logs" collides with the head of an unfortunate pirate and makes a quite audible and very hollow, unwooden "bonk". It's hilarious.
* Obvious fake rocks used in ''Film/SevenChances'', where the hero performs a memorable IndyEscape down a hill.

[[/folder]]

[[folder: Live Action Television ]]

* In the ''Series/StarTrekTheNextGeneration'' episode "Ethics", [[TheWorfEffect Worf's]] spine is broken when a cargo container falls on him. It seems almost humourous, since the way it falls and bounces indicates that it's so light it wouldn't even hurt a human, let alone a big sturdy Klingon.
** There's another example in the [[Series/StarTrekTheOriginalSeries TOS]] episode "The Return of the Archons": A melon-sized "rock" bounces off a stuntman's head and he keeps running. Apparently it wasn't supposed to hit him at all, and was left in under time pressure.
* ''Series/StargateSG1'' has an episode with a flashback which reveals how Daniel Jackson's parents were killed. Apparently, they were crushed to death under the collapsing walls of an ancient cardboard temple.
** It was also parodied rather hilariously in the ''Wormhole X-Treme'' episode when they kept pelting the Jackson-analog with the "bricks" in multiple 'takes'.
* In ''ElChapulinColorado'', it's not only rocks but literally '''everything'''. El Chapulín hits an enemy with a chair, and you can actually see the styrofoam right there.
* {{Nickelodeon}}'s ''LegendsOfTheHiddenTemple'' and ''[[NickelodeonGuts Guts]]'' were made of this trope. They were {{game show}}s for children, so it would have been disturbing if the effect were more convincing.
* This occurred in the series finale of ''SmallWonder'', when Ted gave a literal meaning to the term CardboardPrison. He offered to pay for the damage, but the movie director said there was no money in the budget for it.
* A common staple for ''PowerRangers''.
* ''Series/DoctorWho'':
** This occurred in several early stories, but most notably in "An Unearthly Child" and "The Daleks." It was a variation in that rocks and rock walls were made of the stuff; the DVD of "The Daleks" points out where Ian accidentally pulls off a chunk of the rock face (!). It's entirely forgivable because the show was at the time confined to Lime Grove Studios.
** "The Dominators" features a scene where the Quarks enslave the Dulcians to do manual labour lifting rocks. There are extended scenes featuring some of the most melodramatically-acted styrofoam lifting ever committed to video. It's especially funny when the Dulcians buckle under the weight and collapse and the rocks bounce around all over the place like tennis balls.
** In "Robot", the newly regenerated Fourth Doctor performs a BrickBreak. The brick prop looks good, but later in the scene he bats it to the ground in a tantrum and the impact makes the distinctive sound of balsa wood.
** The Ogri in "The Stones of Blood" are a whole alien race of this.
** The piece of fallen rock crushing the Master in "Logopolis". Anthony Ainley's acting does a good job of conveying the weight, but when Tom Baker moves it he clearly cannot be bothered to pretend it's heavy and just tugs it up casually with one arm.
* ''Series/MysteryScienceTheater3000: {{Gamera}} vs. Guiron''. When a building collapses on the kid heroes, the SOL crew point out how little it looks like bricks.
-->'''Tom Servo:''' Maybe [Guiron] can help us clean up this styrofoam.
* ''Series/{{Viper}}'' Episode "Cold Storage". Two people are running away from an explosion. The Rocks flying around are out of Styrofoam. They have been broken and you can clearly see the white unpainted inside of the Rocks.

[[/folder]]

[[folder: Western Animation ]]

* Played with on ''WesternAnimation/PhineasAndFerb''; When they are constructing their life-sized replica of Niagra Falls, Ferb (on the ground) picks up a boulder and throws it all the way to the top of the structure. Phineas says that [[LampshadeHanging even though he knew that that was papier-mâché]], the throw was ''still'' very impressive.
* Used in-universe in an episode of ''WesternAnimation/TheLegendOfTarzan''. Tarzan freaks out when he sees a seemingly helpless actress about to be crushed by an avalanche, and rushes to save her. However, the actors show him after the scene that the boulders were actually fake ones that are incredibly light.

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