DANIEL RADCLIFFE: Michael, I found out that Ralph Fiennes split his soul into 7 pieces and scattered them around the world. And yes, this really is what I learned, not the set-up to an RPG on Super Nintendo.
A thing that a character needs to obtain in order to cash it in later for a Plot resolution.
For example, let's say that our intrepid hero must steal a key, then find the Treasure Chest of Galumphry that the key will open, then remove the Orb of Power from the chest and use it to banish the Big Bad. The key, the chest, and the Orb are all plot coupons. Extremely common in video games, where collecting these coupons is known as a Fetch Quest, it is often presented as collecting several pieces of a lost artifact or gaining recognition from several factions.
A plot coupon might just as easily be one item in a series of MacGuffins, where the things themselves are not important, it is the seeking of them that moves the story along (indeed, the two terms often get used interchangably). See also Sword of Plot Advancement.
If the items in and of themselves are useless and only become valuable in hindsight, see It May Help You on Your Quest.
If the goal of the mission is to obtain an item that turns out to be less valuable than the finding of it, Its The Journey That Counts.
Coined by Nick Lowe in a science fiction convention talk, later printed as an article The Well-Tempered Plot Device in the fanzine Ansible and popularized by the Turkey City Lexicon.
Every Story Arc of Sailor Moon had one or more of these. Most notable are the Seven Rainbow Crystals...especially since they weren't in the original manga and were created by the anime specifically to extend the storyline. In the manga they're just looking for one big crystal; in the anime it breaks into seven color-coded pieces so the senshi have to spend that much longer trying to find them.
The five Weapons of Light in the third season of Slayers; most of the time, the one we see is the Sword of Light wielded by Gourry. And it isn't just for the third season either, the Sword of Light is the key to a lot of storyline events.
.hack//ROOTS intially has a set of items that the Twilight Brigade were collecting because they think it will lead to the Key of Twilight. Ovan claims that the items are leftover data from the previous iteration of The World and have no ingame purpose anymore. They turn out to be the breadcrumb trail for a trap laid by Yata but there's also no reason to assume Ovan's explanation is wrong since he had to fool Yata about not recognizing the trap but being interested in the items.
The Ark of the Covenant, the Sankara Stones, the Holy Grail, and the Crystal Skull in Indiana Jones
Also the headpiece of the Staff of Ra, Grail Diary and Grail Markers.
Subverted in The Matrix: Revolutions when Trinity provokes a Mexican standoff rather than fetch "the eyes of the oracle" in order to save Neo from the Merovingian
The Death Star plans in Star Wars: A New Hope. Luke's original quest was to get them into the hands of the rebels.
The Percy Jackson and the Olympians: The Lightning Thief movie features the titular character, Percy Jackson, and his friends Grover and Annabeth following a magical map given to them by a guy who's clearly very trustworthy to find three magical pearls that will let them escape from the underworld. In the books the three pearls are given to Percy by some water Nymphs, via his father. In contrast to the book, the movie seems to miss the lesson the books set up by having Percy leave Grover, his best friend in the underworld, abandoning him. Then again, I'm pretty sure no one making the movie had actually READ the book, so that's not much of a surprise.
The hero's medal in Wreck It Ralph. Ralph needs it to win a modicum of respect among the Nicelanders, and the first major plot point is his adventure through Hero's Duty to retrieve it (within Hero's Duty, it's a MacGuffin). Unfortunately, it gets stolen by someone who cashes it in for almost exactly the same reason. Then the main plot starts.
In Teresa Edgerton's The Grail and the Ring, the titular grail. (It is not the Holy Grail, but a grail carved out of a single large sidhe-stone, a substance that grants it magical powers.) Subverted in that Prince Tryffin, when tracing the object's history in the Inner Celydonn, actually collects a "shadow" of the grail, not the original. It's strongly implied that Dame Ceinwendisposed of the original in the Marches-Between-Here-and-There to keep it from making any more trouble, then couldn't find it again when it might have been useful.
Justified in Bridge of Birds by Barry Hughart — the story is structured as an elaborate, carefully-scripted quest, and it turns out that there's a reason why it's structured that way.
Lampshaded and double-subverted in Un Lun Dun by China Miéville. The book of prophecy claims that, in order to defeat the Big Bad, they must collect a chain of these. The initial subversion comes when the protagonist decides this will take too long, and skips to the last link in the chain. The double-subversion comes when she realizes that she actually needed the Plot Coupons after all. Fortunately, she is able to Take a Third Option to get around this.
Emily Rodda's Deltora Quest series and its magic gems (plus other random broken pieces of something in the sequels.)
In Harry Potter and the Deathly Hallows, Harry has to track down two sets of Plot Coupons before he can finish off Voldemort. The second set was strictly optional, but as long as Voldemort's already looking for one of them...
"Don't get cute." He grinds the gun barrel against the back of my neck. "The encapsulated bird your conspirators sent you to fetch. The sterilized male chicken with the Creator DNA sequences. The plot capon. Where is it?"
EVERY book in the Rainbow Magic series has one of these. No exceptions.
Inverted in Roger Zelazny's Forever After, in which the group of heroes who originally gathered the five sacred weapons/armor pieces, must return them to hiding, to keep the world from tearing itself apart from the strength of the combined energy.
Zelazny's Changeling had the hero going on a quest to find the three pieces of his father's magical staff, the only tool powerful enough to defeat the villain.
Coraline had to recover the souls of three dead children as part of the game to escape the Other World.
Live Action TV
Mocked in the Angel episode "Reprise," wherein Angel is told that to get to the Big Bad, he needs a ring; to get the ring, he needs to kill a certain demon; to kill the demon, he needs a magic glove. Angel cuts off his informer with, "Okay, now you're making this up."
The long-running T-Bag series, whose 9 series and 4 specials consisted of nothing except chasing plot coupons (first letters, then numbers, then whatever arbitrary things the writers came up with). And hanging lampshades on them.
Subverted in the Doctor Who episode Last of the Time Lords: The Doctor's companion Martha spends an off-screen year assembling a super-gun and set of super-bullets that can kill a Time Lord permanently. As soon as she's done it, the Master captures her and destroys it; Martha later laughs at him for believing in such an obvious plot device and reveals that her search was just a cover for her real mission.
Although the real mission required her to find everyone on the planet. Sort of counts.
Done straight when the Fourth Doctor spent an entire season chasing the segments of the Key to Time.
Just about every Rambaldi artifact from Alias (very evident in season one).
Supernatural : The four rings from the Four Horsemen of the Apocalypse form a key that will allow Sam and Dean to re-imprison Lucifer.
Prison Break uses this repeatedly, with varying effectiveness. Coupons range from a specific bolt to all sorts of evidence about the Company to the five million dollars that DB Cooper stole and buried in Utah.
In one episode of Star Trek: Deep Space Nine, Jake and Nog end up trading one plot coupon for another in a seemingly endless chain. 5000 wrappages of yamok sauce, for 100 gross of self-sealing stem bolts, for seven tessipates of land...
In Albion, a long quest revolves around finding (of all things) a virility amulet for a tribal king (and saving the guy who made it, who got lost in a big dungeon). Then there's the Metal-Magic Scroll and the High Knowledge which are required for a spell that is pretty much the only thing that can defeat the Big Bad.
The Jiggies in Banjo-Kazooie, which are used to complete the jigsaw puzzles in Gruntilda's Lair to open new worlds. Used again in Banjo-Tooie as proof that you are worthy to complete the challenges of Jiggywiggy, who seems to be the master of all things Jiggy. Naturally, these challenges open up new worlds.
The parts of Dracula's body in Castlevania II: Simon's Quest, again in the inverted castle portion of Castlevania: Symphony of the Night, and a third time in Castlevania: Harmony of Dissonance.
Almost every Sonic game has used the Chaos Emeralds (or "Time Stones" in Sonic the Hedgehog CD) as plot coupons. In the earlier games, they were not necessary to complete the game, they just made it easier and gave you the good ending. However, since Sonic Adventure, they have, in nearly every game, been necessary elements of the plot, often being the goals for completing the level.
Used in most Commander Keen games (ship parts in Invasion of the Vorticons, guardians in Goodbye Galaxy!, bombs in Keen Dreams).
In Act II, you must collect the Viper Amulet, the Staff of Kings, and the Horadric Cube to assemble the Horadric Staff, which acts as a key to open the tomb of Tal Rasha.
In Act III, you must collect Khalim's Relics; combined, they act as a key to open the Durance of Hate.
In Dragon Warrior/Quest IV and sequels, the player must collect the 4 legendary armaments (sword, shield, helmet, and armor). Only the hero may wear them, and by the time the player acquires these, his hero likely already has better equipment.
In the flagrant Dolled-Up InstallmentDragon's Lair: The Legend, Dirk quests to collect the Lifestones to awaken a sleeping giant knight. Specifically, 194 of them. It's as much fun as it sounds.
The music notes of Harvest Moon: Magical Melody and the harvest sprites of Harvest Moon DS
Kirby games generally have a set of special stars (or Crystal Shards in the game with that title) that you must collect to actually face the real Big Bad — who will only show himself you complete everything else. However these items are generally used to make the weapon he needs in the final fight.
The Legend of Zelda and its various sequels are the namesake for this trope. In later games, there are often two sets of coupons, the first usually being three items (pendants, pearls, etc.) needed to claim the Master Sword, rewarded halfway through. The second act then has a set of more items (medallions, pieces of a mirror, etc.). Another is simply eight items (essences, pieces of the Triforce of Wisdom) without any distinct midpoint
Mario & Luigi: Partners in Time has you collecting the six pieces of the shattered Cobalt Star. Played for laughs in this one, as the number of shards you have goes up and down wildly throughout the game, until you get them all which is worse than useless; it actually frees the Final Boss).
The 3-D Platforming Mario games also use this trope. Super Mario 64, Super Mario Sunshine, and Super Mario Galaxy all have you looking for 120 stars. In Galaxy, you even have to get them all a second time to with Luigi to unlock the 121st star for the 100% completion. However, none of these games actually require you to get them all to see the ending.
In Super Mario Galaxy 2, you also have to collect 120 stars and then find 120 more green stars to unlock the Grandmaster Galaxy, which has the last two stars, leaving you with a grand total of 242 stars for 100% completion. In both Galaxies, power stars are justified as being fuel.
Taken to the extreme in New Super Mario Bros 2: The game wants you to collect 1,000,000 coins (regular coins) for no apperent reason. If this is achieved, it then challenges you to find 99,999,999 coins (enough to fill the coin meter with all 9's, basically). You are then rewarded with a new title screen.
Each Metroid Prime games has a set of items that must be collected in order to access the final level. Fortunately, neither Metroid Prime or Metroid Prime 3 force you to get them in the main quest, and Prime 2, despite having a set of keys for The Dragon of each energy controller (which aren't Plot Coupons themselves), only told you to find them when you needed them, many times along with you doing something more important/interesting.
The big exception here are the Octoliths in Prime: Hunters, where you must find them all at very specific plot points, and in a specific order.
Each game in the MOTHER series features Plot Coupons. However, only the first game actually had you collect anything, and that's in the loosest sense of the word.
MOTHER1 features the Eight Melodies, or the 8 parts of a song that the mysterious Queen Mary of Magicant has forgotten. The Melodies aren't actually items. Instead, various NPCs or Items sing them to you, you even get one melody from a cactus. In order to proceed to the Big Bad, you have to sing all eight melodies to Queen Mary. It turns out that Mary is actually Maria, Ninten's great-grandmother, who was abducted by aliens. Gigyas was a baby she volunteered to raise, and the song you have spent the whole game learning is a lullaby she used to sing to him. Singing the lullaby to Gigyas is the only way to actually defeat him.
Mother 2/EarthBound features Your Sanctuaries, eight locations where Earth's Power was the strongest. Each also had a melody associated with it, and when Ness uses the Sound Stone to play them all back, he goes to his own version of Magicant. Unlike the first game however, the eight melodies, nor the power of Magicant are used against Gigyas. Paula has to pray nine times instead.
Mother 3 features Seven Needles scattered across the Nowhere Islands, which require the use of PK Love to be pulled out. Pulling out all seven awakens a sleeping dragon that the islands rest upon, who will only listen to the person who pulls out the seventh and final needle. The Big Bad eventually reveals a mysterious masked general who can use PK Love as well, and uses him to try and pull out the seventh and final needle. The Final Battle takes place at the site of the final needle.
Dark Souls has the Bells of Awakening, that must be rung to reveal the purpose of the Undead. And then, after that, you retrieve the Lordvessel and then kill some gods for their Lord Souls.
Most Bioware games are, to a large extent, about retrieving plot coupons rather than the plot itself: In Knights of the Old Republic, the player has to find all Star Maps to get behind the villain's military strength; to retrieve these Maps, he always has to do something that involves finding out about the game's background and/or solving problems unrelated to the actual plot, like a Wookiee civil war or a conflict with Tusken raiders. The main plot will only go on after finding one of these coupons. Dragon Age: Origins has the player finding a few rather large coupons in the form of allied armies - to get these, he, just like in KOTOR, has to solve several local problems unrelated to the main plot. In Mass Effect 2, most of the game revolves around finding living breathing coupons aka squad members - the actual plot is few and far between and only moves on after gathering a certain amount of members.