Shadow of Impending Doom

If you're in a cartoon, an anvil, safe, or piano can fall on you at any time -- often without warning. But when comedic effect demands, your imminent flattening can be several seconds away, portended by a Bomb Whistle and the slowly expanding Shadow of Impending Doom.

As this shadow - often circular - engulfs the soon-to-be-crushed (an especially large anvil or rock may darken the entire scene), it will be met or ignored with a number of stock responses (such as wondering why it got dark so early). a particularly oblivious flattenee clapping the dust off his hands in satisfaction of a job well done, while the merely stupid will watch in confusion as their partner or adversary flees the scene; if he does notice, there's a good chance the falling object is far to big to escape -- expect him to simply stand there, resigned to his fate, perhaps looking to the sky in bug-eyed terror, perhaps producing a tiny umbrella or sign reading "Eep!" On rare occasion they might run back and forth within the shadow, too panicked to think to actually leave it. Note that this implies both that the object is falling down perfectly straight and that there's light directly above it.

Of course, the character could try to escape, at which point the anvil will either follow him somehow(with or without the shadow updating) or land on a sloped surface and slide toward its target. But rest assured, those caught in the Shadow will meet their (temporary) doom.

Anime and Manga

 * The Ranma One Half villain Herb orders his super-strong minion, Lime, to crush Ranma with a boulder. There's an amusingly cartoony Beat Panel of female-Ranma, pig-Ryoga, and duck-Mousse looking up in shock while a gigantic round shadow is cast over them.

Film

 * In Avatar, the Leonopteryx, a flying Apex Predator, is known to the Na'vi as Toruk, which translates to "Last Shadow" in English.

Video Games

 * Not a cartoon use per se, but several boss encounters in World of Warcraft feature plummeting meteors or other forms of messy death that must be avoided by players; this is usually advertised by an obvious visual effect on the targeted area several seconds before anyone within it goes splat. Players who die repeatedly due to failing to move out from under the Shadow of Impending Doom tend to get laughed at by those with sharper reflexes. Some memorable examples include Kael'thas Sunstrider's Flamestrike, Kil'jaeden's Armageddon, Kel'thuzad's Shadow Fissure, the Twilight Fissure used by Sartharion's drake minibosses, Flame Leviathan's multiple Kill Sats, Hodir's ice stalagmites, Freya's solar beams, Mimiron's rockets, General Vezax's shadow crushes, rocket launchers during the battleships encounter, viscous goo thrown by Putricide during Festergut's hardmode encounter, sudden lack of markers for same goo thrown by Putricide in his own battle and exploding cluster slime bombs during Rotface battle, back to visible markers for vortexes of the Blood Princes, ice geysers during Valithria encounter, Sindragosa's frost bombs and Lich King's Shadow Traps.
 * The Legend of Zelda's Wallmasters show the shadow of their hand before they strike from above and take you back to the dungeon's start.
 * Interestingly, you can normally roll out of the way if you're quick enough, or if you can find a ladder, the shadow disappears entirely.
 * One of the minigames in the first Rayman: Raving Rabbids game involves walking a blindfold bunny around a small landscape full of cartoonish instruments of pain, and scoring points for every misfortune that befalls the miserable protagonist. The target score is 51,000 points, and the player might soon discover that this is a tall order indeed, for the scores awarded for blundering into a cactus, or for stepping on a rake or perhaps walking into a beartrap, are generally a matter only of a few tens. It's then that the player notices the Shadow of Impending Doom at the centre of the game area, which is gradually growing larger and larger. The payoff comes when a colossal 50,000 ton weight crashes down covering the entire arena, awarding 50,000 points on the spot...
 * In the 2D GBA Duke Nukem game, one cutscene has an alien guard standing outside the secret base Duke is being held in when it blows it up. He finds himself in the shadow (Though due to poor graphics, it looks more like he turns black) before a chunk of the base falls on him.
 * Later on, when Duke drives a jumping tank around, he can run down alien soldiers, or jump on them, cloaking them in shadow as they look up at Duke's falling tank.
 * This is becoming a common mechanic for third-person perspective 3D games to warn you of impending danger. The Sly Cooper series, for example, warns you of everything from eagle attacks to giant sea monster tentacles by showing a (shaped!) shadow where they will strike. Of course, these shadows have no bearing whatsoever on where the approaching objects are, when you consider the sources of light which would be casting shadows.
 * The Toy Kingdom boss from Sonic Advance Trilogy had several attacks like this.
 * In Mario & Luigi: Bowser's Inside Story, a shadow appeared when something huge was about to fall on Bowser. First it was his castle (which might I add, is the size of a mountain and made of solid stone), then it was a giant tower mecha's foot (whereupon Bowser tries to recall what happened last time the shadow appeared, but got squished before he figured it out). Whenever Bowser gets squishinated into a pulp, he goes giant and kills whatever squishified him.
 * Any and most Flying enemies from Super Mario Galaxy 1 & 2 usually had a shadow when they were preparing to attack. Most notable may be the Bowser fights in SMG 2 in which you're on a small planetoid, and as Bowser is preparing to punch the living daylights out of you, a bright orange shadow appears under his fist.

Web Comics
"Namazu: I am big and ugly."
 * 8-Bit Theater provided us with: "That's odd. The thief's almanac didn't say anything about there being a total eclipse of the "
 * Not to mention the time when Black Mage had the entire continent of Australia dropped on his head by Sarda.
 * Homestuck: John tosses his newly-acquired (worth a million boondollars) into his  The porkhollow is sadly aware of the growing shadow.
 * The shadow of a Colonel Sassacre book is later seen looming above.
 * Touhou Nekokayou Used in this strip. Everyone except Komachi failed to notice.
 * Touhou Nekokayou Used in this strip. Everyone except Komachi failed to notice.


 * Girl Genius has one cast on right before he's crushed by a pillar.

Western Animation

 * Just about every cartoon made back when violence was the plot (Looney Tunes et al.)
 * Probably Wile E. Coyote's specialty, especially the tiny umbrella and sign gags.
 * SpongeBob SquarePants:
 * In "Musclebob Buffpants", a referee at an anchor tossing contest keeps getting hit by anchors. At one time the shadow actually follows him around as he scrambles for cover.
 * In "Spongeguard on Duty", SpongeBob claims to be as cool as lifeguard Larry, "and if I'm not, may I be struck by..." he is interrupted by a roll of thunder, so he switches to "... a flying ice-cream truck." A shadow then appears over him, accompanied by chiming.
 * Also, right before the truck was about to hit him, Spongebob played it safe and shouted "AND LIVE!" The truck conveniently stopped in mid-air right above him as he said this, then fell on him.
 * Family Guy contains a nice subversion/variation of this. One of the cutaways shows a man on the 6th of August 1945 in Hiroshima. He first gets a parking ticket and then a car speeds by, causing him to get stained by mud. He then asks "How can this day get any worse?" We then see a shadow falling towards him together with the noise and the man proclaims: "Oh my God!"