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. 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. Examples of Shadow of Impending Doom include: