Necessary Weasel



""Be happy that weasels infest the world. Weasels are like motor oil for society. It wouldn't be fair to judge motor oil outside the context of an engine. If you put motor oil in your mouth, it would be filthy and slimy and leave a bad taste. But when that oil is inside an engine, it does an important job and you're glad it's there. Weasels are the same way. Slimy and disgusting, but essential.""

- Scott Adams, The Way of the Weasel

As a logical extension of Tropes Are Not Bad, many tropes that might otherwise come across as gratuitous, offensive or just plain wrong in most genres are considered not just accepted in certain genres, but is practically a part of the genre. Complaining about the simple use of the tropes (as opposed to particularly offensive variations) in said genres is rather short-sighted and pointless, since, well, it's in almost every other work in the genre.

Can often be the cause of an Enforced Trope. Some Acceptable Breaks From Reality are Necessary Weasels to particular genres as well. Contrast with Bad Writing Index, an article listing some real (versus merely perceived) flaws.

Artistic "flaws":
 * Rule of Cool in general; "realistic" does not always equal "interesting."
 * More Dakka, Stuff Blowing Up in summer action films.
 * The lack of plot, characterization or logic in Pornography.
 * Gorn in Slasher Films.
 * Blatant Wish Fulfillment and Mary Sue characters in Fairy Tales and mythology.
 * Author avatars in Web Comics, especially Gaming Web Comics.
 * God Mode Sues in combat-oriented video games.
 * Toilet Humor in comedies featuring babies.

Implausibilities:
 * Faster Than Light Travel usually present in space-based Science Fiction and virtually all Space Opera.
 * Aliens Speaking English, whenever the plot is not about first contact with them.
 * Artificial Gravity, for "soft" Science Fiction works.
 * No Conservation of Energy in portrayals of Stock Super Powers.
 * Ignoring of the Square-Cube Law (as well as other laws of physics) in Superhero, Humongous Mecha, and Attack of the Fifty Foot Whatever stories, as well as some types of Starfish Aliens.
 * Instant Expert in Role Playing Games.
 * Benevolent Architecture -- what are the odds that a video game character's surroundings will always be perfectly suited to that character's unique powers or abilities? Or, for that matter, that wreckage will always form a path, rather than an obstacle?
 * The Perry Mason Method: Because once the audience knows who the real culprit is, there's no real reason to continue the story.
 * Hitbox Dissonance in Bullet Hell games - otherwise they'd be impossible rather than just Nintendo Hard.