The Law of Conservation of Detail

""There's also a guy with a unique sprite there. So you know what THAT means.""

- Chibi Soma's Megaman Battle Network 5 walkthrough

Every detail given is important.

We have 42 minutes. If we give a detail, it better be important.

Oh, sure, we can set up a Red Herring or two, but we had better expect the viewer to attach importance to any detail we let loose in the plot. Shame on us, if we later expect the viewer to be surprised by the importance of the detail we let slip.

Although conservation of detail tends to be particularly pronounced in a "compressed" medium like a weekly television show, it is a proper and useful tool for creating fiction in all media, filtering out irrelevant detail to make time for actual plot. There is a fine line between good World Building, and rambling on about pointless crap. How come people on TV always find a parking spot right outside their destination? This is why.

The law can be applied to video games as well. If any detail of the game requires a significant investment of time to develop, it will be a primary detail. One-off NPCs rarely ever get anything more than a generic sprite/character model, have only the most basic walking animations, and have no name. You can tell that a character will play some role in the plot if they have an unusually complex character model or a headshot next to their dialog (unless plenty of other characters have that same headshot). Plotwise, this serves to separate Round and Flat Characters.

Since artists create video game worlds from scratch, scenery also obeys the law. Say they set a level in a supermarket; a real one stocks thousands of products. In the time it would take to design all that non trademark-infringing packaging they could make several entire games. So they use a handful of designs over and over. Fortunately the trope works to their favour: we accept less detail because it is not central to the game.

This trope has probably caused more Epileptic Trees than every other trope combined -- Dying Dream notwithstanding, as people expect things to have a reason.

Sometimes we see the payoff for a detail later, but we are still not done with it: it will prove to be important in a different way later still: the writers have used Chekhov's Boomerang. The predominant use of Chekhov's Boomerang is to let the writers surprise you.

See also Chekhov's Gun, Chekhov's Gunman. Contrast Nameless Narrative. Responsible for One Degree of Separation and Everyone Is Related. When writers deliberately take advantage of this trope to overwhelm and confuse audiences, see The Walrus Was Paul. Combine this with Rule of Symbolism, and you get Everyone Is Jesus in Purgatory.

For the drawing equivalent of this trope, see Rule of Animation Conservation. For the nonhuman equivalent, see Rule of Personification Conservation. When an adaptation removes explanatory details to save time or attention, see Adaptation Explanation Extrication.

When a work flouts this trope and contains lots of little asides that are not necessary, that is Narrative Filigree.

Warning: May contained unmarked spoilers.

Anime and Manga

 * Football manga Eyeshield 21 does this with every team the main characters go up against. Except for the protagonist's team, every team consists of a few dozen generic nameless players whose faces are usually hidden behind their helmets and two or three important named characters. The latter are inevitably the stars who make all the big plays. You can tell how important a team will be to the story by how many players get names; the first team they play, for example, gets one named player, and after that game they never impact the plot again. Meanwhile, important recurring rival teams get five or six named players, plus coaching staff.
 * One Piece
 * There is a short arc about a giant whale who had been waiting for fifty years for its pirate friends. It ended and was never mentioned again, and everything could have just been another sad but heartwarming episode. Then, more or less three hundred chapters later,
 * Lots of old characters, mainly villains, from, were freed from Impel Down and became decisive to plot development. To the amazement of the readers: If you check carefully, his face had already been shown in a single panel of a side flashback almost five hundred chapters before.
 * Mahou Sensei Negima has a lot.
 * The shaking of hands of Theo and Ricardo. There are four important people in the picture. The two foremost people are the Princess of Hellas and a Megalomesembrian Senator and the other two are the Captain of the Ardiane Knights and
 * Chizuru's membership in the astronomy club.
 * Makie's lack of worries about life turn out to have plot relevance later on.
 * Ala Alba symbol appears repeatedly dozens of chapters before the group is officially formed.
 * When the series is still pretending to be a standard harem series -- every once in a while we see some of the more supernatural girls (mostly Kaede, Eva, Chachamaru, Chao, and Setsuna) just sitting off to on the sidelines, since they don't have any interest in such silly activities.
 * In 20thCenturyBoys, perhaps the only thing that doesn't gain major significance later in the plot is the seven year old son of one of the protagonists.
 * Subverted in episode 2 of Death Note. Light spends a good chunk of the episode setting up and explaining an elaborate safety mechanism to hide his notebook, and it never comes up again. Instead, the pay-off is more immediate: it gives the audience a quick introduction to Light's personality.
 * In the manga, when he notices that someone (the people who installed the cameras) entered his room from the state of his no less elaborate door safety mechanism, he infers that they didn't find the notebook because the fire trap didn't go off. His solution to the problem of the cameras is considerably less elaborate. "Hey Ryuk. Go find the cameras and I'll give you some apples."
 * Steins Gate utilizes this trope to the full extent. Every single character actions that were shown will have some kind of significant effect.

Comic Books

 * Dropped all over the place in Sandman. Seemingly minor details end up being plot-centric on a second read.
 * The seemingly innocuous phrase "I have my responsibilities..." that Morpheus is fond of invoking early and often in the series ends up being such an integral statement of his personality that he.
 * Early in the series, Desire says in a seeming throwaway line that s/he'll "Bring the Kindly Ones down" on Morpheus. That's precisely what happens, though not in the way Desire planned.
 * Used to good effect in Jeff Smith's Bone. A map that Smiley Bone finds by random chance in the first issue ends up

Film
"Harry: "I'm so sorry. That was a terrible scene. It's like, why was that in the movie? You think it'll come back later? Hmmm...""
 * Parodied in Kiss Kiss Bang Bang, when the narrator sarcastically points out the importance of a conversation in his story.


 * Used very well in Back to The Future, which disguised its plot points as jokes.
 * Used to create tension in the final battle of Iron Man. When Tony creates his original power generator, he observes that it could run "something big for 15 minutes."

Also, the "icing problem."
 * Wayne's World - Chris Farley's unusually knowledgeable security guard.
 * The Incredibles: the moment Edna Mode starts making a big deal about capes being caught in things, you know that someone else is going to experience a very fatal wardrobe malfunction by movie's end... unless you've read Watchmen, in which case you might write it off as a Shout Out. The costume for the baby,
 * Citizen Kane - Playing with this trope is arguably the main conceit: it's a movie about the impossibility of finding the right details. "Rosebud" is an example, as is the famous "girl in the white dress" speech.
 * Timecrimes. From the moment Clara appears on-screen, pay attention. Any detail that seems out-of-place will get explained or otherwise become an important plot point.
 * The Big Lebowski takes this trope and throws a coffee mug at it.
 * All the Saw franchise, especially the first one (remember when Jigsaw mentioned having a disease?). The last thirty seconds of each installment usually review such details and make the audience feel proud or ashamed depending on whether they'd realised it previously or not.
 * Done exceedingly well in Shaun of the Dead and Hot Fuzz (made by the same people), in which almost every line of dialogue either foreshadows what's to come or gets repeated in a meaningful way.
 * ...or as a Brick Joke.
 * In the German movie, The Lives of Others, when the main character hides his typewriter (he was writing anti-government pieces in Eastern Germany), he notices that his fingertips were covered with the red ink he used. At the end of the movie,
 * Used masterfully in Rango, the climax of the film has the title character use a Chekhov's Armoury to
 * In Megamind there are  which all become revealed to be important later.

Literature

 * Thursday Next - In Jasper Fforde's Something Rotten, Thursday is showing Hamlet around the "real world" when she is almost injured/killed by a random accident. She explains to him that, while in the Book World (fiction), this would certainly turn out to be an important clue to something later on, in the real world, such events are meaningless. Because Something Rotten is fictional, it does turn out to be an important clue to something later on.
 * In The Belgariad by David Eddings
 * In the historical-perspective prologues of the very first book, Pawn of Prophecy, mention in passing as the location Torak did some stuff... only for  10 books later.
 * At the beginning of Pawn of Prophecy, the first book, the old storyteller brings out . Lo and behold, halfway through the fourth book   The old storyteller, being Belgarath himself, knew the entire time.
 * Also in Pawn of Prophecy, Garion mentions to Belgarath in a throwaway line that . Funnily enough, in book 5,.
 * Lots of "masterful" literary works are called so due to complete aversion of this trope. The lady passing on the street is described in extreme detail and is never seen again.
 * If someone is invited to a banquet in Romance of the Three Kingdoms, then chances are that it's part of a plan to kill them. Most of the banquets without murderous intent go unmentioned, leaving modern readers to wonder why anyone would be stupid enough to go to a banquet in the first place.
 * Douglas Adams is famous for mentioning things in throwaway lines which later turn out to be what the entire plot hinges on. However, he does a fantastic subversion in Dirk Gently's Holistic Detective Agency (which is itself a book of this trope) - there's a scene where the protagonist is looking into a bathroom, and Adams spends several paragraphs describing the contents of the room, the panelling on the walls, the scuffs on the floor, and so forth, in intricate detail, only to end with "There was also a large horse in the room, taking up most of it."

This trope may also have been parodied with a fictional novel that Arthur Dent reads on the planet Bartledan: Due to a plumbing problem that is only briefly mentioned in the second chapter of the novel, the main character abruptly dies in the penultimate chapter (the rest of its precisely 100,000 words are about road-mending). "He asked if he had any money with him, to which Don Quixote replied that he had not a farthing, as in the histories of knights-errant he had never read of any of them carrying any. On this point the landlord told him he was mistaken; for, though not recorded in the histories, because in the author's opinion there was no need to mention anything so obvious and necessary as money and clean shirts, it was not to be supposed therefore that they did not carry them, and he might regard it as certain and established that all knights-errant (about whom there were so many full and unimpeachable books) carried well-furnished purses in case of emergency, and likewise carried shirts and a little box of ointment to cure the wounds they received"
 * Adams also explains the use of this trope in So Long And Thanks For All The Fish, stating that "It makes for big fat books such as the American economy thrives on, but it's boring."
 * Subverted in the book series Personal Effects. The main gimmick of the series is that it encourages the reader to follow up on details mentioned in the books - calling the phone numbers gives you voicemails, and all the websites actually exist. The first printed book even comes packaged with a bunch of handwritten notes and pictures.
 * Tom Clancy tends to fight this tooth and nail. Paragraphs will be spent describing things other authors would just gloss over. He does love his Technology Porn.
 * Ignored in Joe Haldeman's The Coming. The story follows a lot of characters, most of which ultimately do nothing for the plot. (Seriously, there was even a porn actress thrown in.)
 * PD James' detective novels featuring Adam Dalgleish feature an insane amount of back-story on almost every character. Everything you need to know is in there, but so are an awful lot of things you don't need to know.
 * The Dresden Files GOOD GOD! Every trope on This Index Will Be Important Later appears in the later books. And each time it is fully fleshed out.
 * Subverted repeatedly in Hawthorne's The House Of The Seven Gables.
 * One of Gors criticisms is that John Norman averts this with densely worded depictions of structures, ships, weapons, down to counting the beams and explaining their practical and cultural significance. He also subverts this, as one detail buried in several dry paragraphs can come back as a plot point or a Brick Joke that will go over the heads of readers who skip those portions.
 * The Count of Monte Cristo: Averted big-time
 * Harry Potter. Enough said. One can wonder whether Rowling loves to re-read her book before writing the ending to insert plotline clues into seemingly trivial details.
 * Don Quixote: This law is invoked by the Innkeeper when he and Don Quixote discuss at Part I Chapter III the need for money being a Knight Errant who is Walking the Earth, and helps to deconstruct those tropes:

Live Action TV

 * Parodied on the DVD commentary for the final episode of The Office (UK). Gervais and Merchant lampshade the "Secret Santa" game, commenting on its apparent insignificance to the plot, and how it definitely won't become relevant later.
 * In an episode of Charmed Prue finishes talking with someone in her office, that person leaves and then the coffee girl (who we've never seen before) arrives, gives her coffee which had apparently been ordered, receives a compliment, and the scene ends. Yeah. The feeling "why did they just show us a scene of someone receiving coffee" was pretty strong, but it did help remember the coffee/sandwich girl character for when it turned out that, without her knowledge, she was actually.
 * Star Trek Deep Space Nine - Played straight during a series regarding the Dominion, which was mentioned in passing in the first episode it showed up in and

The extra material on the DVDs even makes note that they were first mentioned in a Ferengi episode, where fans expect nothing to have a lasting effect. "Mickey: I knew we should have turned left!!"
 * In the episode Time's Orphan it's done a bit heavy handed when Keiko gives little Molly a shiny silver bracelet and the music swells for a moment before going back to normal. Guess what feral Molly is wearing when they pull her back from the past?
 * In one episode of Goosebumps we see the parents of a kid protagonist working on something. It turns out.
 * Used judiciously on Monk. Every single random detail comes into use. Character pronounces a word differently? Clue. Has only an aunt for family? Clue. Orange juice jug empty? Clue. Bike comes with a lock? Clue. Meanwhile, the protagonist's skill is noticing and remembering everything, even though he sees more of his world than the viewer and it thus doesn't follow this trope for him. A viewer aware of the trope can still use it to guess the answers before him.
 * Same for CSI about everything being a clue.
 * Psych takes it to a whole new level though, by zooming in and highlighting the clue (or flashing back 10 seconds to some relevant thing someone said) while Shaun makes his squinty-I-just-saw-a-clue-face (as Lampshaded by Gus when he eventually points out that he sees many of the same clues Shaun does, but doesn't need to make a face about it).
 * How I Met Your Mother - A fan theory regarding the identity of the mother relies on this trope. In season 3, Ted
 * This could be deliberate misdirection
 * Seinfeld did the opposite and focused on silly things(like the parking spots mentioned above), yet it was still funny. Curb Your Enthusiasm after it, however, was completely made up of small details and barely had anything else, which is why it is awesome.
 * Doctor Who exudes this trope. Vote Saxon was one particularly devious detail given, foreshadowing the final arc. The same thing happened with Arc Words "Bad Wolf".
 * In the Season Four episode, "Partners in Crime", the taxi that was meant to pick up had an ATMOS sticker on the front, foreshadowing.
 * It may just be nothing, but in Season One, Mickey Smith finishes one of Captain Jack's anecdotes for him:


 * The Leverage team needs to create elaborate schemes in order to manipulate their mark. This means that side comments to the mark often end up being important later, and their importance becomes apparent during the "how it was done" flashback scenes. This is a trait shared with it's spiritual predecessor Hustle.
 * On one episode of 24, Jack is captured and forced to give bad tactical information to CTU. He ends the information by declaring he is in a "flank-two position". Given that the series is all about time constraints, it's reasonable for viewers to assume that any apparently-innocuous dialogue that's not Techno Babble is important. In-character, the terrorists holding Jack just assume its standard tactical talk. Naturally, it turns out to be the duress phrase. Except that CTU changed the duress phrase since Jack was last part of it, and they barely pick up on it before it's too late.
 * Lampshaded constantly on Jonathan Creek in which the titular detective notes apparently pointless bits of general knowledge which become crucial in solving the mystery. At one stage, after ascertaining that an elderly client buys fish-food at a market and getting a baffled look in reply, The Watson wryly comments: "Don't worry, it'll have some deep significance that is invisible to us mere mortals."
 * In Eureka, any and all interesting new technologies presented or talked about early in the episode is inevitably going to turn out to be either A) part of the cause of that week's crisis, or B) part of the solution to said crisis.
 * On a time-travelling episode of Smallville Clark and Chloe walk through the busy work-space of the Daily Planet in which their collegues are partaking in some rather noticeable activites: someone gets a huge bouquet of flowers, someone else trips over, and so on. The camera lingers on them the first time around so that Clark can accurately describe their activities to Chloe when the time-travel kicks in and he needs to convince her of their situation (that the day is repeating).
 * On an episode of Once Upon a Time, Kathryn bumps into a character we've never seen before at the school, and the camera dwells for a moment on his confused face. Back in fairytale land, he ends up being her true love: a knight turned into a gold statue, whose face was hidden beneath a visor up until the end of the episode.

Tabletop Games

 * A very common mistake for new Game Masters who will vaguely describe a room, but go into minute detail about one feature of the room. All Genre Savvy players will immediately gravitate towards this item. This can also be used intentionally, by only describing a certain part of, or item in the area, you can ensure that everyone notices it.
 * One RPG group went by the tenet that 'Any woman or plant the GM bothers to describe is a trap.' The GM caught on and ran them through an adventure that could roughly be described as 'The Magic Greenhouse Land of Amazons'.
 * Similarly, whenever the DM makes a hidden roll or asks for a spot or listen check (that they fail), the players will assume something is going on and, if they're bad metagamers, try to act on it. Incidentally, few things unnerve a player as much as rolling really well on a spot check and being told, "No, you don't see anything of importance..."
 * Paranoia recommends that Game Masters occasionally roll the dice for no reason other than making the players nervous.
 * Risus too in order to help with improvising off what the players speculate the roll was for.
 * Dungeons and Dragons occasionally uses this trope to explain why all the magic and gear seems designed for folks crawling into caverns, killing ugly people, and taking their stuff. The local magicians probably do make magical plows to help farmers, magical compasses for navigators, and so on. However, since players don't care about most of this stuff most of the time, let's cut back to the stuff that will affect the world as players experience it.
 * Ebrerron outright states this in its campaign setting.
 * One article of Dragon Magazine was dedicated to listing such mundane magic items.

Video Games

 * Since every object in a game has to be created from scratch rather than in movies where the world conveniently exists already, it's inevitable in video games of all types with regard to the environment. There simply aren't the resources in terms of textures or manpower to create, say, five hundred unique cars, or thousands of different books to fill a library that only makes up part of a single level. Some games have started creating procedural plant life and mooks, but man-made products are likely to always be subject to this trope.
 * Any newspapers you see will always be either the cover or a single page with a story relevant to the game, even if they're supposed to be random pages blowing in the wind.
 * Books will usually be relevant to the plot or at least relevant to its message; an evil doctor might have fifty copies of Frankenstein lining his various shelves, for example.
 * Industrial equipment will usually look brand-new and catalog-fresh, with no signs of wear and tear and everyone mysteriously using just one brand of any given piece of equipment.
 * Buildings that aren't falling down for plot reasons will look like they've just been finished and certainly never lived in.
 * In any game without an inventory system (and many with), no matter what is displayed on a vending machine, using or destroying it will cause it to dispense exactly one type of product, usually cans with no discernable logo.
 * If you're going through an office, any desk, office or cubicle which contains significantly more objects than normal will belong to a character important to the plot in some way. This also tends to apply to houses in Adventure Towns. If not, the clutter will be part of a puzzle of some kind.
 * People have an odd habit of barricading any rooms of their house you don't actually need to visit, often using their inexplicable collection of identical furniture. This works even if the furniture and doors are wood and you have a gun that one-shots tanks. Alternatively, a Master of Unlocking might be part of your team to only open the doors that actually have things behind them.
 * All guns use the same types of ammo. If you do get ammo for a gun you don't have, you'll have a chance to acquire it later. Even uncommon types tend to be just lying around in plain sight. Any given type of ammo will be in the same type of box, and any gun cabinets will be unlocked. If it is locked, you'll need a puzzle to find the key, instead of just finding the owner, or their body. Strangely, gun cabinets tend to the same types of problems encountered with barricaded doors above.
 * In Dragon Age Origins, if a party member didn't have an approval bar he wouldn't be a permanent party member.
 * Subverted in Dragon Age: Awakening where they introduced Mhairi, a potential Grey Warden. Before the game got released she got treated the same as any other character, receiving her own trailer and character page. When you play the game, she has an approval bar and can gain XP. All this trouble
 * This is similar to the character of Ling in Grand Theft Auto Chinatown Wars who was prominently featured in promotional material, has a spot on the box cover, and has her own character bio at the official website, so it's a bit surprising that she's killed off as soon as you meet her.
 * Subverted with the first generation of the Pokémon games. There's a one-of-a-kind truck in the game (vehicles aren't seen anywhere else in the game since the preferred methods of travel are walking and flying or surfing on Pokémon) that can only be seen under very specific conditions at a certain point in the game before being Lost Forever (although there are ways to return to it later in the game); a very high percentage of players would not see it while playing through the game. Endless rumors were sprouted about the truck, such as finding a Mew there, etc.; however, the truck actually had no real significance at all. The rest of the series just follow this trope in every possible way.
 * Persona
 * In Persona 3 Portable, the PSP rerelease of Persona 3, a random faceless character was added in the game's bar/night club. He makes some pretty ominous statements throughout the game, but the last thing he says near the end of the game is followed by a portrait. This leads fans to believe that due to the Law of Conservation of Detail, he is important. Turns out he's a character named Vincent, protagonist of an Atlus psychological horror game titled Catherine.
 * Persona 4 exemplifies this trope. Every little nagging detail has meaning -- every detail. The guy who gets rejected by Yukiko at the beginning of the game? The council secretary who is having an affair?   The TV announcer he was having the affair with?   The bumbling detective who can't keep his mouth shut?   The gas station attendant you shake hands with in one of the very first scenes?   The list goes on.
 * Subverted with Ziegfried in Final Fantasy VI; the character is interesting and appears throughout the game, but is completely unimportant. This characteristic has its own entry on The Grand List of Console Role Playing Game Cliches. Ziegfried's Contradiction: Just because someone is weird doesn't mean they're important.

Square's been subverting this trope since the first Final Fantasy. Coneria Town, the first city you can visit, has a well that you can inspect: "This is a well. You might think that there is something to it... But in fact it is just an ordinary well."


 * The infamous '1/35 Soldier' items in Final Fantasy VII ("Collect all 12!") were hard to find more than a handful of and had no function (also the 'Custom Sweeper'). In a game famous for its confusing translations, these may have been supposed to be actual toys in-universe.
 * Suikoden
 * In Suikoden you can tell in the games who is one of the 108 Stars: If they have a portrait and a name, they're a Star (or a villian, but those are often the same thing).
 * Subverted in Suikoden II, however. There's a character with a portrait and a name (Ellie) that is neither a Star nor important to the story at all. She exists for one reason: In the quest that's unlocked if you load Suikoden I data at the start of the game,.
 * Subverted in Chrono Cross. Of the portraits that characters have, forty of them are playable characters, five of them are alternate versions of the playable characters, and twenty six of them are NPCs. Of the NPCs, one is unimportant: a shopkeeper you meet early on. Throughout the game you become convinced she'll be important, but she never does, being the only one of the Loads and Loads of Characters who isn't.

The shopkeeper, however, is related to Funguy. Every single NPC with a character portrait seems to be related to one of the PCs.
 * Avoided in Metal Gear, Snatcher, Policenauts and anything Hideo Kojima does, because of his obsessive-compulsive insanity. He cannot stand to not worldbuild. The only people who care about the incredibly elaborate tragic backstories, sex lives and namedropping pertaining to characters who show up once and then die - and the endless infodumps about guns and items and nuclear weapons and the future and useless metagame trivia - are going to be fanfiction writers. For the most part, backstory events will be mentioned inconsequentially to add a little flavour to a character.

For example, Hideo Kojima designed every desk in the first Metal Gear Solid separately. Every sigle desk! You have to respect a man who puts in that much work. And at least in Metal Gear Solid Kojima-san was nice enough to let players skip all that and go right to the neck-snapping if they want.
 * The entire Ace Attorney scene is all over this, up to the point of being Anvilicious. Every piece of evidence - besides the lawyer's badge, etc. - is always used at least once. The problem is using the right one, because you need to use them as a sort of sentence fragment to answer questions. Players soon hit on the idea of saving before a particular point they don't know how to get through, and just trying out every single item.

Similarly: profiles in Justice for All and Trials & Tribulations. The lawyer's badge gets used once or twice outside of the courtroom. You even had to present the screwdriver, which had importance exactly because it has no importance at all, which throws suspicion on the suspect's reasoning for having Edgeworth personally pick it up in the first place.
 * In the first Resident Evil game, there's a single empty room in Jill's storyline. No puzzles, no items, no enemies. Turns out it's only important in Chris' scenario.
 * One Sega CD role playing game would say things like "Who would talk to a cow" if you talked to the cow, as all role players will do. Also mentioned "Wow the guards and castle are laid out exactly the same in this castle as they were in the last one. Maybe that is to show how the two kindgoms are very closely tied, or maybe the programmers were just lazy."
 * Averted in the Elder Scrolls series, most notably the more recent offerings. The sheer amount of useless items dropped into the environment (paintbrushes, mugs, flatware, etc.) threatens to boggle the mind.
 * Being on the same engine, the 3d Fallout games do the same. However, a shrewd player will be able to tell important items from the rest of the Vendor Trash and Cow Tools that litter the level. The older ones had TV dinners, popcorns, nuka-colas, pocket lint, and others that do nothing but take up space in your inventory. You can also examine rocks. Do it enough times and your character will cry out in frustration.
 * Near the beginning of The Legend of Zelda Majoras Mask we find a masked character that manually opens doors unlike every other NPC in the entire game. This tiny fact foreshadows just how long his particular sidequest will go on for and how import he really is.

You also get a notebook that is useful for sidequests -- of which the game has many. Any NPC who appears in this notebook after talking to you has a mask to give you. Characters that do not appear in the notebook are not important for sidequests, though they may still be important to the plot.
 * Subverted in Mega Man ZX Advent due to its attempts to avert You All Look Familiar, where everyone you meet has different designs and personalities, except for the guys in uniform, who still act different. In other words, trying to rely on this trope to see who is important is completely pointless for this game. Though, as in all Mega Man games, the only ultimately really important ones are the robot animals/things actively shooting you.

The Battle Network series is a strong example. Since there seem to be Only Six Faces used for all the generic NPCs ever, anyone with a unique sprite is bound to have a NetNavi that you will eventually fight and/or befriend. It is particularly noticeable in Battle Network 5, since you are in the process of building an anti-terrorism task force; if you're told to be on the lookout for a new member, expect the very next place you enter to have an NPC with a unique sprite, and expect that exact same member to be the operator of the next Navi to join your team. "You see a bar patron.
 * Ace Combat
 * Ace Combat 04: Shattered Skies mission "Deep Strike" is set in an area with a ravine leading from the target area back to the RTB line. After splashing the targets, you get notice that Stonehenge is firing your way and have to take your plane below 2000 feet in order to make it out of the area. The only way to do that? Why, the ravine. It also shows up in the "Megalith" mission. Those other missiles within reach aren't just for show.
 * X: Skies of Deception is also in love with this. It's particularly obvious after you play both halves - or, in one case, all three thirdths - of a Remixed Level. Most of them.
 * In Fire Emblem, almost all enemy or NPC with unique sprites and more then a few lines of dialogue is either a boss or recruitable. Which is understandable, considering how many enemies you end up facing.
 * The Godfather: The Game subverts this. There are various places that appear different on the map, many a locked door... While some of them are indeed significant, quite a few of those are Red Herrings that aren't of any consequence whatsoever, even in sidequests.
 * In Grand Theft Auto IV, the dirt bike seemed to be an incredibly useless bike: not as fast as the speed bikes, not as cool-looking as the choppers, not as cool-sounding as any of the bikes. But, provided you choose the right storyline, Niko uses a dirt bike to chase  in a helicopter. (Needless to say, the dirt bike also enables a Crowning Moment of Awesome).
 * Used in a different way in the first two Fallout games. The point-and-click aspect leads to a prevalence of "examining" objects similar to Wasteland. Therefore, even if the character sprites are the same, a player can tell the difference this way. Upon examining two men in leather jackets, you might see this:

You see a short, stocky man. He has the confident, relaxed stance of an experienced fighter."

"--You see a large pile of rocks."
 * Also used hilariously for innocuous items that aren't really meant to be examined. Upon examining a pile of rocks:

- You keep a close eye on these rocks, in case they move to attack you.

"Alice: Hey, Villager A, come over here.
 * Subverted in Knights in The Nightmare. The added artbook gives details on all of the units and all of the knights, including age, personality, relationships with the other knights, and character portraits. This is actually important to using the transoul feature.
 * Subverted in Dragon Quest IX. The world map is a fairly large place, but not all of it is covered with interesting things. A lot of the dead-ends are covered in item gathering points, and eventually you find maps to grottoes, randomly-generated dungeons that are invisible on the world map until you "search" them with the A button. However, most of these grottoes rarely stray far from the beaten path, and a noticeable amount of areas on the world map end up never becoming the slightest bit notable. The Eastern Stornway area is particularly empty; the enemy encounters there are nearly identical to the Western Stornway area, there's very few grottoes in the area, and a single item-gathering point (seashells, on the southern stretch of beach). The bulk of the Eastern Stornway area, including the entire northern beach, remains unused.
 * Played straight with characters, though. Plot-important NPCs generally get 3D sprites. Generic ones are all 2D sprites, recycled throughout the game.
 * Lampshaded in .hack//. Several characters wonder why the graphics in the Hulle Granz Cathedral are so gorgeous when there's absolutely nothing there. The Cathedral is in fact one of the most important areas in the entire franchise (every single story has something important happen there), but within the context of the Game Within a Game, there really isn't anything there.
 * In Ar Tonelico II, you can tell which characters are important to the plot because they have full-body pictures used when they speak; everybody else has only a small sprite. This leads to strange situations like a visible character speaking to an "invisible" one, or identifying a character that turns out to be very important later during an otherwise innocuous scene.
 * Many an Urban Legend of Zelda was started thanks to this trope. Back in the day, when more rudimentary technology meant a much stricter enforcement of this, people took it for granted that only the important stuff would get detailed. So as technology got better and developers started averting this trope for the sake of providing a richer gaming world, gamers payed attention to neat but nonessential details (e.g. the Mario character portraits seen through a window in Ocarina of Time) and thought that they had some greater significance.
 * Modern Interactive Fiction loves this. One-room games where the player must use everything in the room are common--if there's a wad of gum in the trash can, sooner or later that will be an important wad of gum. From playing these games, audiences come to expect this, too, making it a self-fulfilling cycle: If your game mentions the walls, players will get mad if the walls aren't fully implemented.
 * In Monster Girl Quest, other than kings and other rulers, only the monster girls get any paper dolls (the rest are just human-shaped blobs of colors), and they're usually the only ones with names as well. Like many other tropes in the game, this is lampshaded.

Villager A: Why would you call me that when I have such a glorious name? I'm Cervantes!

Alice: I don't care."


 * RPG Classic Divine Divinity takes this trope and uses a sledgehammer to destroy it. It contains innummerable amounts of plot-unrelated or useless things like kitchen ware, pictures, junk and all sorts of other things that can be bought or sold for no reason or moved around yet not used for anything useful. It also contains a lot of books, most of which are highly entertaining short stories and at least two longer series, one about an Ork pirate and his adventures. Others show spells and demon summoning or are about the ingame world, describing plants, animals and monsters.
 * Averted in Shenmue. The town is full of buildings you can enter and characters you can talk to, but only a handful of them are important in any way.
 * Averted in Dreamweb - there's plenty of items you can take, but the most of them are useless, and would just clutter your inventory. (things like plates, cups, lighters, and so on)
 * Averted in the Deus Ex series, there's dozens of characters you can talk to that have no impact on the plot and serve no purpose, and there's lots of virtual books that are interesting to read but don't really serve any actual purpose.

Webcomics

 * In El Goonish Shive the author had intended for a one off character(the principal of a school specificaly) to have a massive scar and eyepatch. Due to this law he chose not to since he had no explanation planned for them.
 * Goblins - A strip introduces a prominent glass window on an inn. Prominent and shiny. MinMax is forbidden to smash it. There is exactly zero chance the window will remain intact.
 * Invoked by Gabe in a Penny Arcade strip where, while playing Skyrim, he insists on carrying 270 pounds worth of BROOMS because he didn't "want to get to the fucking Broom Dungeon and be, like, "why didn't I pick up all those brooms?"!"
 * Homestuck. Every detail is either important or will later get reused for a Call Back or Running Gag. Every. One. And there are a lot of them.

Western Animation

 * In Winx Club season 3, viewers expected that Chimera being a fairy studying at Beta Academy would become important, and complained about plot waste when it proved otherwise.
 * Subverted by Pixar with the Pixarpedia - even sub-minor characters, such as nameless, faceless, do-nothing bystanders get an entry in the encyclopedia.
 * A similar case to the Pixar example for My Little Pony Friendship Is Magic: Everypony, even five-second gag characters, has at least their own Fan Nickname, Wiki sub-article, and can even be promoted to join the long list of Ensemble Darkponies.
 * There are many random mutants released from Genosha in the Slave Island episode of X-Men. Except they aren't so random at all, seeing how Mystique is one of them. The Blob is also there, and several others who will become important in later episodes.
 * A Gargoyles episode started with Brooklyn making a remark about mosquitoes. While that alone was unusual, by the time a second one was mentioned, it became obvious they will be vital to the plot.