What happens when The Glorious War of Sisterly Rivalry switches genders? Cain and Abel. What's the difference between The Scrappy and a Creator's Pet? Authors love their Pet. Is this introductory paragraph trying to explain by example a Xanatos Gambit or a Batman Gambit?
When defining a trope, it often helps to establish its similarities, differences and relationship to other tropes; a common convention on this site is to refer to some tropes as Sister Tropes.
When two or more tropes have some overlap in their descriptions, "parentage", or use, but not enough for one to be a Sub-Trope or Super-Trope of the other, these are called Sister Tropes. That is, both have a similar form or function, either by category (character, plot) or by effect (characterization) rendering them both similar but distinct enough to be considered equals. Not that there's anything wrong with subtropes!
These are the four Trope Sisters, each more lovely than the last:
- Function: When two or more tropes serve the same function, but are notably different in execution.
- Form: When two or more tropes are similar in style but themselves unique, usually used for different purposes.
- Same Parent: Subtropes of the same Super-Trope are frequently referred to this way.
- Conjoined Use: They are different, perhaps a character and an attack, plot, or relationship, but see frequent (though not necessarily exclusive) use together.
Sometimes when two distinct tropes serve almost exactly the same function or have very subtle differences in description, it can reach the point that they are used almost interchangeably. Bad Flanderization! Bad! The Canonical List of Subtle Trope Distinctions is your friend.
- It is possible to juggle a Villain, Idiot and Conflict Ball all at once. Idiot Ball doesn't necessarily make direct conflict, and Conflict Ball doesn't necessarily make idiocy. Thus they are related, but not really covered by the other. Villain Ball carrying may involve stupidly Pyrrhic Villainy and cause conflict aplenty, but it doesn't have to.
- Big No and Chewing the Scenery (or Large Ham) can often overlap, but not always.
- Impractically Fancy Outfit is a cause of the Ermine Cape Effect, but the latter trope is also responsible for the continued application of the former.
- Royals Who Actually Do Something and Lady of War occasionally overlap.
- Lethal Chef and It Tastes Like Feet are sister tropes.
- One Judge to Rule Them All and Golden Snitch are sister tropes.
- So are Gargle Blaster and Hideous Hangover Cure.
- Cast of Snowflakes is what happens when those Loads and Loads of Characters are given characterization.
- Nice Job Breaking It, Herod, your Genocide Backfired on us completely.
- Human Shield and Bulletproof Human Shield both deal with bystanders being used to protect a target. The former discusses the psychological coverage, while the latter deals with physical protection.
- High Octane Nightmare Fuel is related to Nightmare Fuel, but it's basically something deliberately horrific that works, rather than unintentional. And when it fails, it's Nightmare Retardant.
- Evil Twin, Evil Counterpart, Evil Knockoff, and Criminal Doppelganger are all about evil duplicates of one person, but the evil persona in the individual tropes are an identical twin, a persona from an Alternate Universe, an intentionally created duplicate, and an Identical Stranger, respectively.
- Descending Ceiling and The Walls Are Closing In are both Death Traps that threaten to squash/crush characters trapped in them, but have different parts of the room move to achieve this.
- The Ace and Parody Sue are closely related concepts with different intentions and execution. Both are (usually) played for comedy, but while the former is an idealized character who's over-the-top nature is played for laughs, the latter is a Take That against a fandom in general.
- Innocent Fanservice Girl and Shameless Fanservice Girl. Both are girls who have no nudity taboo. But one is aware of the existence of nudity taboos, and the other isn't.
- Badass Normal and Costumed Nonsuper Hero often overlap in certain contexts (most importantly probably the person of Batman), even though the only thing they conceptually have in common is having no superpowers.
- Xanatos Gambit and Batman Gambit are both schemes to achieve benefit but they are executed differently. The Batman Gambit is based on Flaw Exploitation and/or what a given mark is most likely to do. Thus, it will fail if the mark doesn't behave as predicted. The Xanatos Gambit is based on Morton's Fork: it can succeed no matter which prong the mark is impaled on. The benefits may be completely unrelated or they may be different paths to the same goal as long as every reasonable outcome benefits the planner in some what.