"I know! That's what I told 'em, but no! All the cruddy exposition goes to me! I've got to talk and talk and fiddle with the computer and talk some more and fiddle and talk! I feel like Obi-Wan cruddy Kenobi!"
Madara in Naruto. He's got a tendency to drop in and explain the plot as needed.
Dr. Inez Fressange of Martian Successor Nadesico abuses this trope to the point of parody: she is actually acknowledged as the "explanation woman" by the whole crew of the Nadesico battle spaceship. There have been cases where she senses her explanations are needed from several rooms/decks over, and she once uses exposition as her talent in a beauty contest.
Mazinger Z: Professor Yumi is both The Professor and The Mentor, so he frequently explains to the characters -and the audience- plot points. He was the one guessed first what was Mazinger-Z and who had created it. He explained how Dr. Kabuto had discovered Photon Atomic power and Alloy-Z and built Mazinger-Z with them. He narrated how Dr. Kabuto met Dr. Hell and what happened in Bardos Island. He recognized Minerva-X and explained what she was and how she worked. He explained what were the Mykene and where they came from... And often during the series he explained what strategy the enemy or Kouji was using, how worked the Mechanical Beasts' weapons... or simply what kind of training Kouji was undergoing. In Mazinkaiser he retained that role (he recognized Mazinkaiser as soon as he saw it, he explained how they had modified to Mazinkaiser in the movie...)
Tokyo Mew Mew: Ryou and sometimes Keiichiro. A hilarious example of this occurs with Masaya in the first episode of Tokyo Crystal Mew. He even feels the need to describe what he looked like in his Deep Blue form.
Subverted in FLCL by Commander Amarao. He tells Naota (and the audience) that Haruko is searching for her lover Atomsk, the pirate king (the scene is accompanied by a humanoid fire creature). Amarao was just guessing, Haruko really wants to eat him.
Tsubasa Reservoir Chronicle: Yuko Ichihara ends up becoming the Ms. Exposition before she is temporarily removed from the story. When she returns in Chapters 216 and 217 were pretty much her exclusively explaining what the hell's been going on.
Suzumiya Haruhi hangs a lampshade on this; Kyon, the sarcastic narrator, constantly tells Koizumi, the Mr. Exposition character, that he talks too much and no one cares what he has to say.
Yu-Gi-Oh!: Every single character in the 4Kids dub, often to downright ridiculous lengths. Everyone feels compelled to remind one another (i.e. the viewers) of the continuous effects of every card in play, the effect of a card that has already been played before in an episode (especially "Monster Reborn"), all the way to what happened two minutes ago. This expo-speak always happens at the start of episodes, (referencing previous events), which wouldn't be a bad thing if not for the fact that each episode includes a "last time, on Yu-Gi-Oh!" opening bit. Also always occurs after a commercial (because, well, you know), but sometime even for no reason at all. As an example of the last type, pick any duel in the Battle City finals/semi-finals and count how many times the fact that one of the characters possesses an Egyptian God Card is mentioned. For the truly ambitious, drink every time it's mentioned, and kiss your liver goodbye.
Subverted in the movie when Kaiba interrupts Pegasus' exposition of a card-effect with "Do you ever shut up?"
Also Lampshaded in one episode where an opponent starts to explain the effects of Painful Choice before Kaiba cuts him off with "I know what the card does, you fool."
GX is especially bad with card exposition. For example, Pot of Greed is used, and explained, in nearly ever single duel. Sometimes more than once.
And that's with a card anybody who's played the card game for some time already knows the effect of. Meanwhile, we only get skimpy explanations of more interesting cards' effects...
Rex Goodwin in Yu-Gi-Oh! 5Ds. There's a reason fans of 5D's use the term "Rexposition"
ZEXAL really loves this, at least in the first few episodes. Everyone that isn't duelling is only present to explain the rules to the viewers. Even Yuuma gets this treatment in the first episode, when he sees Shark Exceed Summoning a monster. Yuma then proceeds to explain how Exceed Summoning works to Kotori, who already knows how it works (but the viewers don't since it's a new game-mechanic added in ZEXAL). Later in the next episode, Shark explains with almost the same wording how Exceed Summoning works, right after having summoned his Levice Dragon. And then there's all the other Game Mechanics... Needless to say, the duels in the first few episode almost use more time explaining how to play the game than actually playing the game.
Reversed in Eyeshield 21 in the form of Yamamoto Onihei, ace lineman of the Hashiritani Deers. More than any other player on the sideline, this is Onihei's role, and a running gag is formed around the fact that his analysis has yet to be accurate. It doesn't help that the team he usually tries to predict is one of the most unpredictable teams in the whole of Japan....
Reborn in Katekyo Hitman Reborn!! does this almost every time a battle is plot-important and he happens to be watching. Most of the rest of the cast is guilty of this at various occasions as well, but it's usually Reborn that does the exposition. In fact, it's consistent enough that one can tell if a fight is plot-important when Reborn is nearby by whether he's beating people up or currently being Mr. Exposition. For everything not related to the most recent level-up, there's Ranking Futa, who seems to be a recurring character primarily for random exposition.
Ergo Proxy had a very interesting method of revealing its backstory: the characters ended up in a bizarre gameshow, where most questions and answers were directly related to the plot. The gameshow host MCQ played the part of Mr. Exposition.
Subverted at the beginning. One of the characters is a scientist who had been working on the Gate. She gives us a rather hefty dose of Expospeak to explain the Contractor-related weirdness; however it turns out she doesn't even know who she is. As such, 90% of anything anyone says in the first two episodes is misinformed at best and Blatant Lies at worst.
Later the trope is played straight with Dr. Schroeder, who appears to be the only person on (or off) the show who both has some idea what's going on and is inclined to share.
Ranma ½: At first, it appears that Dr. Tôfû Ono is going to fulfill this role, but it fails to happen, partially because of his tendency to become a bumbling idiot when Akane's sister, Kasumi is around (to the point where he actidentally destroys potential cures for their problems), and partially because of the introduction of the and Trickster Mentor Cologne. To lesser extent, Happôsai. In fact, the manga gave him Chuck Cunningham Syndrome; he vanished by the end of the first Cologne story arc. The anime kept him on as a bit-character and an excuse for filler episodes.
One Piece lampshades this with the character of Sentomaru. He considers himself "the most tight-lipped man in the world," as he is a member of a highly secretive government branch and as such is privy to hundreds of secrets. The thing is, he's constantly blabbing those secrets and often without the slightest provocation. Whenever he does, he'll start by saying something to the effect of "I'm the most tight-lipped man in the world! You'll get no information from me!" and then proceeding to inform everyone.
Fairy Tail had Klodoa, a sentinent staff who spends about three chapters explaining the Oracion Seis's plans. Once he's explained everything he's fufilled his plotline purpose and promptly dies. He's insignificant enough that that's not worth a spoiler tag.
Dragon Ball Z often has exposition but this particular line spoken by Krillin in The Tree of Might recapping what happened moments prior is particularly egregious, especially considering he delivered it while lying on the ground in pain, speaking to absolutely no-one but himself.
Krillin: No! Earth's energy was sucked up by the Tree of Might and Goku couldn't find enough power to form a Spirit Bomb to defeat Turles! Now we're dead for sure...
Tabitha's butler in Zero No Tsukaima spends about five unbroken minutes spilling Tabitha's back story to someone he'd never even heard of before who just happened to show up with Tabitha at her mansion.
Although, perhaps he does this just to counteract Tabitha's natural tendency not to give any exposition whatsoever. She's like a version of Nagato that only sometimes answers direct questions.
Durarara!!'s resident nerdy motormouth, Shinra Kishitani, is usually the first to offer any sort of explanation as of the weirder elements of the series such as "how can Celty see, hear and smell if she has no head" or "how can Shizuo be so damn skinny and so damn strong at the same time?" The only one whoever seems particularly interested in Shinra's hypotheses are Shinra himself, so his explanations are typically either ignored (by Celty) or interrupted with physical harm (by Shizuo).
Sailor Moon: Luna and Artemis tended to work as the ones to deliver exposition, but Ami in particular liked to inform them of their situation during battle... as more of a Captain Obvious than anything.
Tenchi Muyo!: Washu usually is Miss Exposition in the manga, popping in to explain one concept another character mentions to a third character... so when Yoshi uses Big Words when talking to a villain, Yoshi stops his exposition to wait for her. Both he and the villain just stands there awkwardly until Yoshi remembers Washu is on a mission in space, and excuses himself.
Brock from Pokémon (and later Cilan) became this more as the series has gone by. It is very rare for an episode of Diamond & Pearl or Black & White to go by in which no unnecessary commentary is made on the events.
Terryman from Kinnikuman would often explain the various attacks and holds used by the characters. His son sometimes takes up the role in Kinnikuman Nisei. Outside of a match, Meat tends to fill this role.
Akiyama in Liar Game spends a lot of time doing this as he explains various strategies throughout. A rare example where this is completely justified because unless you're well-versed in game theory, studying every panel, and calculating everything with a pen and paper, you'd be left with no idea of what is going on. And even then...
Elsie of The World God Only Knows starts as this, explaining to Keima the nature of Hell and the escaped spirits. Of course, most of what she says is wrong, so when her friend Haqua starts coming around, Keima is quick to go to her for more accurate information.
Kotetsu and Onikiri from Kamisama Kiss. Their main purpose in the story is to provide infodumps when needed.
Sonic the Hedgehog: Nate Morgan used to fill this role, offering pages upon pages of technobabble-laden exposition for the "benefit" of the reader.
The Inhumans in Marvel Comics (at least in their early appearances) are an entire race of Mr. Expositions. They also do recaps. A lot.
The Key, from DC Comics. Lampshaded and subverted in that opening up your entire mind to the universe (A God Am I) has the side effect of causing a lot of monologuing.
Dragon Ball Z fanfic Honor Trip: Usually Cell, but other characters get in on the act, too, especially when they're explaining the science behind some of what's taking place.
Yugi Oh The Abridged Series: Kaiba served this role in Episode 47 when he explained the back story involving his adoptive father and himself.
The Spectre is this in the Justice League/Naruto crossover "Connecting the Dots." To be fair, it wasn't his only purpose, and nobody else had an idea of what was going on, but in the earlier chapters all he did was talk.
Grunnel fills this role in With Strings Attached, but it's justified because he's bored to death and quite happy to chat with the four about anything.
"Beagle John" clarifies some of what's going on in New Zork.
The Hunter also starts out as a Mr Exposition, except that most of what he says is useless, and the four ignore him as much as possible.
Twilight for Phoenix in Turnabout Storm. Some of the stuff she explains to him are common knowledge for fans of the show, other times she explains elements that are new to the audience.
In Inner Demons, this seems to be the only reason that Lezard was included in the story though he later upgrades to Apple Bloom's Love Interest. He knows just about everything about the Queen of Darkness prophecy and ends up explaining everything to the protagonists.
Exposition has not merely vanquished mimesis, it has burned its homes to the ground and sown salt in its fields. It's really bad when Katara is describing what is happening on screen.
Ric Olié in The Phantom Menace has dialogue that consists entirely of exposition such as "That little droid did it, he bypassed the main power drive!" Same thing with Admiral Ackbar in ROTJ ("It's a trap!")
Obi-Wan Kenobi's main role, besides dying dramatically, is to provide backstory on Anakin Skywalker.
Mr. Gibbs in the Pirates of the Caribbean trilogy seems to exist primarily to tell Will about Jack's backstory or pirate lore. He takes it very personally when Those Two Guys, Pintel and Ragetti, try to do his job for him.
In Casino Royale, Mathis plays the role during the poker scenes, explaining what is going on to Vesper. Later, Felix Leiter briefly plays the role by offering to "stake" Bond and then promptly explaining what "stake" means when he looks confused.
Ardeth Bey in The Mummy Returns, which actually is quite at odds with his characterization in the first film. As Stephen Sommers says on the commentary track, "In the first film Ardeth Bey was this cool, mysterious character. Here he's just a chatterbox. Every chance he gets, it's just wave after wave of exposition." In fact, he refers to the character as Mr. Exposition. There's some exposition provided by him in the first one, too. For example, the very crucial fact that you can't shoot Imhotep. And the entire prologue.
Grave-Robber from Repo! The Genetic Opera. His song, "Zydrate Anatomy", introduces himself, Amber Sweet, Blind Mag, some Applied Phlebotinum in the form of zydrate, the veritable epidemic of surgery addiction, and reveals the first of Rotti Largo's many, many plots.
And before that, there's 'Genetic Repo Man' and '21st Century Cure,' both of which go over the basics of the world they live in, explaining the role of Repo Men and some facts about the circumstances that led to the Repo Men coming into existence.
Dune: Adpating the plot of the book was so complex and so much of it was cut from the movie that Miss and Mr Exposition were required: Princess Irulan before the credits, explaining the general setting, and after the credits, the secret report within the guild giving the context for the next scene.
Mr. Universe to the point where Joss Whedon refers to him as The King of Exposition in the DVD commentary.
And River's imaginary/remembered/dreamed teacher explaining about Earth-That-Was and the Alliance and her class commenting on the Reavers.
Lindsay Brigman in The Abyss does a slightly lampshaded version of this in the early descent scene, as she explains the (plot critical) perils of prolonged deep water diving to a SEAL team that is thoroughly familiar with them. They end up finishing most of her sentences for her.
Margo: You mean the Lo Pan that's chairman of the National Orient Bank and owns the Wing Kong Trading Company, but who's so reclusive that no one has laid eyes on him in years? Jack Burton: Who the hell are you, anyway?
In Fatal Instinct, secretary Laura Lincolnberry explains the situation in great detail to her boss Ned Ravine.
In addition to providing keys when needed, the Keymaker provides a great deal of information to Our Heroes about the bomb-trapped office building with many doors (and how to break into it).
The Architect, who did almost nothing but spout exposition.
Another Cameron example is Ripley in Aliens when she provides a briefing to the marines. She basically tries to explain what happened in the first movie, but fails as the marines are constantly interrupting her story, and asking mocking questions. A good half hour later, they aren't in a laughing mood anymore...
Captain Steiger in Patton. He is a German officer assigned to research U.S. General George S Patton for the Nazi high command. Screenwriter Francis Ford Coppola said in the DVD commentary he invented the character as a way of giving out biographical information about Patton to the audience.
The Water Works crew in Batman Begins during the train chase. They were not originally part of the script, but added in to further explain the danger of the situation, and perhaps for visual variety.
McCroskey: I want you to tell me everything that's happened up until now. Johnny: Well, let's see. First the earth cooled. And then the dinosaurs came, but they got too big and fat, so they all died and they turned into oil. And then the Arabs came and they bought Mercedes Benzes. And Prince Charles started wearing all of Lady Di's clothes. I couldn't believe it. He just took her best summer dress out of the closet and put it on...
The World's Most Helpful Guard in the original Clash of the Titans. Perseus, a complete stranger, walks up to him, and he manages to go from surly hostility to explaining the complete social and political history of Joppa in under a minute. While swatting flies.
Ariadne from Inception came off as improbably perceptive because of a somewhat borderline example of this trope.
Jetfire in Transformers: Revenge of The Fallen just does not shut up. His exposition after being introduced is a good portion of the remainder of his on-screen appearance. When he first meets Sam and Mikaela, he rants a solid 2 minutes about the most non-sensical old man banter, like his father being the first wheel made in the Stone Age, and his problems with his mother. Later, he explains almost the entirety of Cybertron's history before the Great War, and only stops when he sacrifices himself to become a Magic Mushroom to Optimus.
Back to the Future series: Lorraine McFly serves this purpose in the first two movies. In Part I, she explains the circumstances of how she and George McFly originally met and fell in love. In Part II, she explains Marty's problem with being called "chicken", and how it got him into an car accident which changed his life for worse.
Doc Brown does a lot of this too, but he's so damn entertaining to watch ("ONE POINT TWENTY ONE JIGGOWATTS!!??") that you don't even notice you're being infodumped.
In The Great Muppet Caper, as Miss Piggy interviews for a job, Lady Holiday goes on at length about her prized jewels and her troublesome brother - both key plot points. This is then lampshaded by the following exchange:
Miss Piggy: Why are you telling me all this?
Lady Holiday: It's plot exposition. It has to go somewhere.
Kindergarten Cop has a "Miss Exposition" delivering a very quick setup at the very beginning as the guy pushes her into a hiding place - he already knows what he's going to tell the Big Bad so there's no reason she should be saying this except to fill the audience in.
Girl: I mean his wife took his kid and a couple of million...
In Wayne's World, Wayne and Garth run into a security guard (played by Chris Farley) backstage at a concert who proceeds to give detailed info about a record executive that ends up being important later. Lampshaded immediately afterwards when Wayne says to camera, "You know for a security guard he had an awful lot of information, don't you think?"
"Okay. We're now officially enemies of the United States of America. Victor is out there somewhere with unlimited power. And we've got a giant intergalactic force that's about to destroy our planet in less than twenty-four hours. Did I miss anything?"
Resident Evil Degeneration: Since he's been in similar situations before, Leon S. Kennedy takes this role the Capcom's (mercifully Alice-free) CG film. That said, he still gets to kick more ass than every other character combined.
In Alien, Ash, being the Science Officer, is the one infodumping the rest of the crew (and the audience) regarding the Alien and the planet it comes from.
Hope: "A fine thing. First, you sell me for two hundred bucks. Then I'm gonna marry the Princess; then you cut in on me. Then we're carried off by a desert sheik. Now, we're gonna have our heads chopped off."
Crosby: "I know all that."
Hope: "Yeah, but the people who came in the middle of the picture don't."
Crosby: "You mean they missed my song?"
Wes Craven in Wes Craven's New Nightmare serves to explain the entire plot to Heather Langenkamp (and by extension the audience). He tells her about the Entity that has taken on the form of Freddy Krueger, that it has been released due to the end of the movie series and is trying to cross over into reality, and that Heather is the only one who can stop him.
Fighting Fantasy: The elderly wizard Gereth Yaztromo often fulfills this role in the gamebooks, most particularly those by Ian Livingstone, explaining the latest evil threat before asking the reader to try and solve it. The reason he can't do it himself, of course, is because he's just too old.
In CJ Cherryh's Cyteen and Regenesis, the first Ariane Emory acts as Ms. Exposition for the second, via pre-prepared programs on Base One left for her successor. In Regenesis, the second Ariane Emory begins leaving records for her successor in a similar manner.
In Simon Hawke's Time Wars books, this role normally falls to Moses Forrester in his initial mission briefings to the Time Commandos.
Subverted in The Wheel of Time: Robert Jordan had stated that several times characters are guessing when giving exposition so you can never tell which Forsaken is the strongest (especially between men and women), or how the hell Mat's dagger actually works. The best example, is in Crown of Swords, where the Aes Sedai accompanying Elayne, and Nynaeve, tell her the Kin are a small group of women who help runaways, and the Aes Sedai use them to find the runaways. Later in the book it becomes clear that while the Aes Sedai are successfully using the Kin at least now and then, they are completely mistaken about the size of the group, when the leaders of the Kin explain that they number about 2,000.
Mike Hanlon in Stephen King's IT. Being the only member of the Lucky Seven who stayed in Derry, and therefore the only one who remembers anything at all about what happened when they were kids, Mike is something of an exposition god in the book. Not only does he provide exposition to his friends little by little, his journal entries provide exposition as to the history of It, and whenever another character gets to do some expositioning they generally turn to Mike and ask if whatever they just stated is correct. Interestingly enough, it works. Contageous amnesia can apparently be a wonderful exposition tool so long as someone is immune.
The Magicians Nephew: Uncle Andrew plays this role initially, until Jadis enters the story and assumes the role.
Prince Caspian: Cornelius, Caspian's tutor outlines how Narnia changed from the situation in the previous book to the current book, and the true nature of Caspian's uncle Miraz.
Erek King from Animorphs. Originally a one-shot Contest Winner Cameo, he evolved into an Ascended Extra and later into this. Years after the series ended, Applegate candidly admitted in interviews that she'd gotten too reliant on using Erek as an expository device.
Dumbledore fills this role quite a bit. From beyond the grave, at one point! Hermione also fills this role on occasion. He basically turns up in some inexplicable magical phenomenom which is barely even given a Hand Wave and says 'Hi, here's a hastily thrown-together explanation to tie up ALL the loose ends so far, by the way, you're not really dead, go finish off the plot now, ya big ol' protagonist.'
Among the trio Ron usually fills Harry and Hermione in on some yet unknown aspect of Wizard culture, while Hermione usually fills Ron and Harry in on some unknown magic they encounter. And occasionally Harry explains to the both of them some new info on the plot, but usually he just sums up Dumbledore's long speeches into neat little packages for the sake of the readers. This tends to distribute the buttload of exposition rather nicely.
Colt Regan: Joseph Cin is a bog standard example, all things considered.
In J.R.R. Tolkien's The Lord of the Rings, Gandalf takes on this role in The Fellowship of the Ring, particularly in "Shadow of the Past" and "The Council of Elrond". (In the latter chapter, however, the role alternates between the various attendees.)
Snow Crash: The Librarian is an expensive computer program owned by the protagonist that is literally an anthropomorphization of all the world's collected information and knowledge, sort of like a talking 200x-size Wikipedia. Its sole purpose is basically to tell the protagonist the complicated plot. There are chapters nearly entirely filled with nothing but the Librarian expositioning.
Several characters in Redshirts. Lampshaded in that, whenever the Narrative takes control, random information about the plot at hand will pop into a character's head, whether or not they have any way of knowing that information, and they will even sometimes automatically say it out loud to their own surprise.
In The Dresden Files this is the main role of the knowledge spirit Bob, with Harry asking "What was that thing that just attacked me?" happening roughly Once Per Book. According to the author, he made Bob inhabit a skull as a joke on a nickname possessed by characters who exist only to explain things - "talking heads". Harry himself also gets to exposit about magic a lot when he's around mundanes.
CJ Cregg, the White House press secretary on The West Wing. She patiently reports every single piece of news, including those with not the slightest connection to the US Government.
Giles from Buffy the Vampire Slayer. In the dream sequence episode "Restless" he even gets to deliver the exposition in the form of a song.
Which is exactly what he's trained to do for many years. Watchers are supposed to tell the Slayer how to kill the evil monster.
Ex-watcher Wesley filled this role on Angel, though the science stuff was shared with Fred.
Deconstructed with Andrew in an episode of Angel. He explains "vampyres" and the nature of Slayers to Angel and his team, much to their annoyance as they already know pretty much everything.
In later seasons, Willow, Tara, and Anya filled this role sometimes, especially if Giles wasn't around — Willow and Tara would exposit about magic, Anya about demons she met in her thousand-year lifespan.
Dawn was heading this way in Season Seven. She even referred to herself as "Junior Watcher" in the finale.
Game Of Thrones: Jorah Mormont; at least in the first season, he mainly exists to inform Daenerys/us about the customs of the Dothraki and other such things.
iCarly: Wendy. Tells the gang that another tv show is stealing their bits. Explains that Freddie gave up a sea trip to get rid of Carly's old friend who was trying to break them up.
At the beginning of every 'Allo 'Allo! episode, Rene breaks the Fourth Wall to explain to the viewer what's been going on. In one subversion he starts off by discussing the doings of some of the townspeople, before saying "You have never met these people, nor are you ever likely to. I am simply giving you the local gossip because with my own affairs I don't know where to start."
Stargate SG-1 has a complete and energetic crew of Exposition People, ready to service your every plot related need. We have:
Samantha Carter, for technological and astronomical info;
Daniel Jackson, for historical, linguistical and cultural info;
In the earlier seasons, Teal'c for Goa'uld and Jaffa info;
And of course we have Jack O'Neill, for all your smart-to-layman translation needs.
Colonel Mitchell even got in on this, excitedly describing the relevant bits of previous missions when similar situations arise. This is most definitely for the audience's benefit since the people he's usually talking to—Teal'c, Sam, and Daniel—were all actually there for those missions.
Guinan became the mouth through which the writers often introduced backstory information, i.e. about the Q, the Borg, etc.
Usually, Data and Geordi did technical exposition, Worf what another ship is about to do/is doing/did, and Troi the emotional state or motives of whatever grouchy alien they ran into that week. In Real Life, exposition to the CO is what each section is supposed to be doing.
Subverted with Data sometimes in that for a long time, Data did not know when it was appropriate (or not) to do the infodumpage.
Data lampshades this in the second part of the very first episode, While reminding the crew of something they should already know, he interrupts himself to say "I'm sorry, sir — I seem to be commenting on everything."
Avoided entirely with Troi because her empathic suggestions were universally uselessly vague. (e.g. "Troi, can you tell why they might be shooting laser death missiles at us?" "I sense... Pain. Pain... and anger.")
Spock: Whatever method we use to stop them, we must make haste. They have only to install some cybernetic devices aboard the Enterprise, and they'll be able to leave orbit. McCoy: How do you know so much? Spock: I asked them. McCoy: ... Oh.
Holly and Kryten in Red Dwarf. Note the redundancy; the producers did, and when they needed to get rid of a character for the sixth season, Holly was Put on a Bus with the rationale that the exposition could be given to Kryten. The writers later found themselves in the same position again, when the newly-introduced Kochanski became Ms. Exposition, and Kryten was relegated to the servile mother-figure that he'd grown out of over the course of the series.
They never really explained why a robot programmed to clean toilets was an expert on GELFs and time dilation in the first place; although this could (and Word Of God says does) explain why Lister remembers the defunct timeline from "White Hole" in "Demons & Angels", when the former episode ends with Kryten explaining he won't.
Joel and the Robots of Mystery Science Theater 3000 humorously pointed this out while watching a movie, labeling two cop characters "Sergeant Exposition" and "Captain Backstory".
In Doctor Who, the Doctor always has a traveling companion from modern Earth who would be in the dark if The Doctor didn't explain everything. That seems to be the main function of the cohort, a "Watson" to his "Sherlock".
Notoriously, the Seventh Doctor, Sylvester McCoy used to hand off the technobabble to his assistant, Ace, who would deliver the exposition in the form of a question, allowing the Doctor to a) avoid learning his lines, and b) nod wisely and say "That's right, Ace. You're learning."
Alfred Gogh and Miles Millar cast Allison Mack as Chloe Sullivan on Smallville because of her "rare ability to deliver large chunks of expositionary dialogue conversationally."
Col. Tigh in Battlestar Galactica (Reimagined) often performs the role of Mr. Exposition, although in one episode, President Roslin subverts this by annoyedly thanking him for his insight. Anders managed to be one of these for one episode, finally explaining what the deal with the Final Five was, as well as some background on the Cylons in general. This being BSG, everything was working against him, and only got about halfway through it. Cavil filled a somewhat similar role in the same episode, but he also didn't spill the beans completely.
Colin Mochrie: Finally, I caught up with you! I'm a mob hitman... They call me Jimmy the Exposition.
Captain Jim Brass, the Homicide detective from CSI: Crime Scene Investigation has been affectionately nicknamed "Captain Exposition" by the fandom, even though all he does is deliver factual data on the victim du jour (such as name, occupation, family, circumstances of death...).
Many of the others as well,on all 3 shows.
All the Supernatural characters have been this at some point, although recently it's been mostly Bobby being the sensible one (most notably, Tall Tales and Dream a Little Dream of Me) and doing the explaining.
Trailer Park Boys: The character of Sara on the Canadian comedy series served this function in the early seasons, explaining many of the goings-on in the trailer park and putting things into context for the audience. Her doing this was justified by the series being framed as a documentary filmed by a camera crew following the main characters around, so it only made sense that the documentary crew would try and find a way to explain things to the audience.
Daniel Faraday fits the bill, though he doesn't quite know everything. Nor does he tell all that he does know. Nor does he think everybody else would understand if he tried. After the episode "The Variable", he becomes a posthumous Mr. Exposition once his journal outlives him.
In season five, his mysterious mother Eloise Hawking suddenly turns into this. "316" opens with a huge lecture by her about how the Island was found, why it's so hard to find the Island, what they need to do to return...followed by a shorter scene where she tells Jack even more detail about why he has to return...
Lois Habiba in Torchwood: Children of Earth. The series attracted many viewers who were unfamiliar with the previous two series, and Lois served to explain the origins of the Torchwood Institute to these new viewers.
Winston in Human Target. Mostly justified, since there's a new mission every week, and someone's got to fill Chance in on the details. There is a certain amount of "Remember, once you get inside..." purely for the audience's benefit though. He's also usually working Mission Control, so it's not his only job.
Gillian Foster in Lie to Me, usually to explain the academic aspect behind detecting emotion to Ria Torres, but to the extent that it often sounds like a textbook exerpt.
On the reality television front, there are scenes on the show Billy The Exterminator that are clearly meant to explain things to the viewer but the way they are explained come in unnatural situations, such as explaining the consequences of not getting rid of a pest to his mother, who not only should already know this, but is the one giving him the assignment from the office. There are also times when Billy and his brother, who also works for the company, are explaining things to each other that they should already know.
Some of the discussion about the history of an item or company on Pawn Stars is clearly designed to give insight to the viewer, particularly in situations where it seems both the broker and the customer should already know what they're being told about the item.
Hannibal on The A-Team would explain the bad guys' plot to the rest of the A-Team and the audience in every single episode.
In the Season 2 finale, "Curtain Call," when Murdock got shot in the shoulder, Hannibal spent the majority of a scene explaining why bits of cloth and such caught in the bullet hole were more likely to cause an infection than than the bullet itself. Then he explained what would happen to Murdock's body as the infection began if they could not get supplies in time.
Merlin has Gaius, the old court physician. He rarely ever has a line that isn't explaining something to someone.
Sometimes the dragon gets in on this trope as well.
Henry from Once Upon a Time is constantly spelling things out. At first, it made sense for him to be explaining things to protagonist Emma, but now it's just straight up talking to the audience.
Future Ted in How I Met Your Mother, usually in order to provide shortcuts to the main plot of an episode by pausing the action to explain a bit of essential backstory to his kids. Varies a lot in its delivery, sometimes segueing to a series of flashbacks or cutaway gags to explain something, sometimes tossing in a tidbit of relevant information (e.g., stopping to tell his kids that Marshall had a temporary filling put in that day, which wasn't seen in the episode, so that the story makes sense).
On Chuck, this job most-often falls to General Beckman.
Brass parodied this at every opportunity. Any character could and would exposit, usually ending the speech "...as you well know".
MythQuest's Max Asher is one. He is a professor of either egyptology or archaeology, but he explains to Brother-Sister Team Alex and Cleo anything they need to know about any myth they encounter.
Horatio Hornblower: The show used written text, explaining the political situation or the situation at sea. Additionally in "The Even Chance", Midshipman Archie Kennedy explains Horatio and the audience his view on The French Revolution and present situation in France ("Louis was captured just before Christmas. What do you think they'll do with him? You can't kill a King." — Oh, Archie!). He also informs us later that the French has killed their king.
The announcers during a match exist to give exposition. They have to explain the holds used in the current match, recap any pertinent information regarding said match, possibly hype any upcoming matches (usually the main event of the show), and be entertaining while doing all of it.
Amusingly, The Dresden Files role-playing game has a skill called Exposition and Knowledge Dumping, a sub-skill of Scholarship. On a successful use, the Game Master can "borrow" the Player Character in order to turn him into a Mr. Exposition about the relevant subject. This actually cuts the middleman out of the traditional RPG knowledge skill check, which usually amounts to "Player makes Knowledge check, GM Info Dumps, Player says 'Okay, I relate this to everyone else'."
Parodied in The Real Inspector Hound by the play-within-a-play's Mrs. Drudge, who answers the phone, "Hello, the drawing-room of Lady Muldoon's countrry residence one morning in early spring?" and "I'm afraid there is no one of that name here, this all very mysterious and I'm sure it's leading up to something, I hope nothing is amiss for we, that is Lady Muldoon and her houseguests, are here cut off from the world, including Magnus, the wheel-chair-ridden half-brother of the ladyship's husband Lord Albert Muldoon who ten tears ago went for a walk on the cliff and was never seen again." And then there's the treacherous fog.
The musical Urinetown, which parodies almost anything that moves, has Officer Lockstock, the narrator, reference this trope on several occasions. Not to forget equally Genre Savvy Little Sally.
Little Sally: Oh, I guess you don't want to overload them with too much exposition, huh. Lockstock: Everything in its time, Little Sally. You're too young to understand it now, but nothing can kill a show like too much exposition. Little Sally: How about bad subject matter?
The Notary in The Grand Duke. In the first dialogue he has a speech stating who the chorus are and what they're doing there, halfway through act 1 he has a song that explains the plot device on which the rest of the show hinges and in the final dialogue he facilitates the ending.
Gringoire in the French musical Notre Dame de Paris (adaptation of The Hunchback of Notre Dame). He spends the majority of his songs singing about the circumstances of the time, only poping into the plot once to almost get hung by a band of gypsies and get married to Esmeralda after she saved him. As soon as that's done, we never see him interact with the other characters again.
Show Boat has in the boarding-house scene an Irish landlady who tells the Beta Couple the longwinded story of how Gay and Magnolia have been doing the last ten years. This exposition proves superfluous when Magnolia comes in and explains her situation in her own words.
Questenberg, servant of the Holy Roman Emperor, in Schiller's drama Wallenstein. Wallenstein lampshades: "Spare us telling us from the newspapers / what we witnessed ourselves in horror!"
BIONICLE has the Turaga elders, who relate old legends about the threats that rear their ugly heads in the first few arcs. Eventually deconstructed; the third or fourth time this happens, the heroes start wondering where they're getting their information and, more importantly, why they're not telling them these things ahead of time.
Pretty much any character who can be communicated with via CODEC in the Metal Gear series. For example, Dr. Naomi in the first Metal Gear Solid goes into in-depth detail explaining the back-stories of all the FOXHOUND members Solid Snake faces, whereas Drebin does the same with the B&B Corps in Metal Gear Solid 4. Ironically, Solid Snake himself serves this role to Raiden in Metal Gear Solid 2.
The Colonel, Otacon, and Mei Ling. and once Slippy all serve this role in Snake's codec conversations in Super Smash Bros. Brawl, explaining information on Nintendo characters that Snake doesn't know about.
This is the sole purpose for the existence of Travis in Killer7. As you go through each mission, he informs you why you're there and what's happened thus far. Since the Killer7 are only called in once things have degraded to where someone has to die, this is essentially Late To The Tragedy embodied in a character. And you can never be sure if Travis (who openly despises you) is telling the truth, either...
Even better than that, while Travis does display open contempt for the Smiths at points, he shows it by being the most honest and trustworthy character in the game. When he says he'll talk "straight up," he's usually getting ready to tell you something you'd really rather not know.
At least he's more trustworthy than Iwazaru. And less annoying than Kess, who tells you how to defeat the next boss.
Maechen from Final Fantasy X. The difference being the fact he doesn't explain the plot. Instead, he goes in long-winded description of the areas you visit for the first time. Nicknamed "Exposition Man" on VG Recaps.
Auron and Lulu from the same game are guilty of this at certain points, but Auron's a Badass so of course you'll listen to whatever he says, right? Right?
Somewhat justified in both cases. Tidus is the game's Watson, and Lulu knows a lot about the world, having gone on two (failed) pilgrimages before accompanying Yuna, and Auron is actually the only character (maybe, aside from Seymour) that actually has any clue what's really going on.
Namine gets this role in Kingdom Hearts II, explaining to Roxas (and the players who haven't played Chain of Memories) just what the heck is going on in the Prologue.
Once Roxas is out of the picture, Master Yen Sid from Fan Tasia serves this role to Sora.
Finally, at the end of the game, Ansem the Wise picks up the role.
In the final chapter of Mother 3, it's revealed this was the entire reason Leder did not have his old memories erased, in case anything corrupts their lives again. His monologue is so big, a stinkbug helpfully memorizes most of what he's revealed if you happen to forget.
Legacy of Kain: Almost every character gets a turn in LOK but none more so than Janos Audron. Every scene with him is part history lesson, part Shakespearean monologue, and part Grandpa's Neverending War Stories.
Morris O'Dell from Splinter Cell gives exposition in cutscenes at the beginning of missions. Justified, as he is a news anchor.
Pick any character with a speaking role in Mass Effect. ANY. CHARACTER. To be fair, most of the time you can just not ask them stuff. ME2 makes this process even more clear-cut; much of the game's extra exposition is on the crew's personal backstories, and they provide those details if you ask. As far as the main plot goes, exposition tends to come from the Illusive Man and the various Cerberus crewmembers, and occasionally Mordin on questions of science. TL;DR: ME attempts to avoid the Mr. Exposition phenomenon by splitting him into about 13+ characters. YMMV on if it worked. There's a LOT of exposition.
As a straighter example, Vigil from the first ''Mass Effect. Explains everything in the game up to that point; what the Conduit is, what Saren wants with it, the fate of the Protheans, and how to stop Sovereign before it's too late.
He was one of these before he even met Jade, though. In his first conversation with Luke, he says "[the headaches] are getting more frequent. They started after you were kidnapped by the Malkuth Empire." Yeah, I'm pretty sure Luke knows that already.
Upon joining the party, Naoto Shirogane in Persona 4 serves this role primarily.
Knights of the Old Republic: Trask, Carth, Bastila, the Jedi, Atris, Atton, Kreia, HK-47, T3-M4, the player character, that guy you run into on Nar Shaddaa...
Kreia gets points for being the main provider of exposition and a Consummate Liar at its worst. The second game in general tended to give the role to people you should never, ever trust.
Kirei Kotomine takes up this role in the Heaven's Feel scenario of Fate/stay night, to the point of multiple lampshadings by the protagonist, who in the narration, complains about the priest's lengthy talks every single time he drops by the church.
Unlimited Blade Works puts Rin in the expository role, while Fate mostly splits it between the two (Kotomine for history, and Rin for the technical side of magic).
The same roles in Tsukihime are filled by Ciel and Arcueid, mostly on the history and nature of vampires in the Nasuverse. None of them are anywhere near as bad as Kotomine, though.
Fleet Intelligence in the original Homeworld had this role largely to himself in cutscenes, but in subsequent games the player-character provided some of their own.
The 10 minute Info Dump in the beginning is apparently narrated by the Bentusi, as is the Final cutscene.
Verdelet the hierarch from Drakengard, though he is also the most useless party member and tends to repeat himself a dozen times per mission. He has only one spell—a "hold" spell, which is only ever used in cutscenes and allows him to turn Caim's pact partner Angelus into the Goddess of the Seal. When Caim tries to make him release Angelus later on, because the seal causes both of them immense pain, Verdelet refuses (along with the entire Union) because doing so would cause The End of the World as We Know It. Caim's reply is to cut him down in between games.
Arena played it straight with that chick who appears in your dreams.
Daggerfall averted it by distributing the exposition over a large number of NPCs.
Morrowind subverted the trope hard by presenting potential Mr Expositions one after the other. Caius Cossades, Azura, Vivec, Dagoth Ur... The kicker? they ALL contradict each other, all the time. There are strong hints that Azura, Vivec and Dagoth Ur have their own motives for lying (or at least not being entirely truthful) and you're never told outright which one was right. A lot is left to personal interpretation.
Rhinehart in the FMV game Privateer 2: The Darkening. Played by a perfectly cast David Warner, Rhinehart's sole purpose (and only scene) near the end of the game is to explain everything to the main character Lev Arris (played by Clive Owen).
Patchouli does most of the explaining in Touhou Labyrinth. She seems to enjoy it too as she acts rather displeased when Eirin takes over the role for one scene.
Monkey Island: This is the main purpose of the Voodoo Lady in the games. Occasionally she'll do some actual voodoo, but usually she's there to tell you what you're supposed to be doing right now.
The Game Of The Ages makes little sense until you meet The Sage who explains the nature of the world.
Bayonetta Subverts this; on the way back from a job, Enzo decides to speak out loud about Bayonetta's nature of having to kill angels every day or she'll be dragged down to hell while she figures out her lost past. A mildly annoyed Bayonetta snaps at him for telling her her own life's story.
Ni No Kuni Plays this straight with Drippy. Because Oliver knows nothing about the world and characters Drippy spends most of his time infodumping Oliver regarding almost any possible subject.
The Ace Attorney series has the various assistants that go around to assist or comment on the action, and to give general plot recaps at the beginning of each chapter. Most often, it has been Maya Fey, though Pearl takes her place a couple times during the second and 3rd games and she is replaced entirely by Trucy in the 4th.
Agent Washington from Red vs. Blue: Reconstruction dispenses all sorts of information about Project Freelancer and the AIs it uses. According to the DVD commentary, Church served in this role for plot recaps in the original series.
It wasn't nearly limited to plot recaps. Burnie (voice of Church and creator of the series) admits in the commentary that he always gave Church most, if not all, of the exposition necessary to move the plot forward since it was always a large number of lines and if necessary, he could always just redo them himself rather than call everybody back in again to do their voices for the nth time to fill in another plot hole he just noticed. The entire rest of the cast (until Washington's appearance) was merely there for comic relief, while Church had the sole duty of carrying the entire plot around on his back. It's no wonder he was always so damn irritable.
Andy, being the only one who can understand the Alien, serves this role in Season 4.
The bard Elan even has a spell called "Summon Plot Exposition" which creates dramatic illusionary pictures that accompany Elan's voice-overs. He also cries when someone else pulls off a good plot recap.
Redcloak often fills this role on the villain's side, with the help of a series of short-lived, lower-ranking hobgoblins (or the Monster in the Darkness).
Mr. Verres from El Goonish Shive, who once exclaimed "I am an endless barrel of exposition!" As the creator explains, Mr. Verres, Grace and Tedd are the main barrels, but since Tedd and Grace learned most of their information from Mr. Verres, he's directly responsible for most of the expositions in the strip. Also, there are Exposition Fairies, but not in the usual sense.
Dream Catcher so far seems to have two. Ooji who really failed to be helpful, AT ALL, and Mr. Relecross who seems to know more
Parodied with Dr. Viennason in Sluggy Freelance. His DVD series "A Visual Guide to Timeless Space" gives pretty much all the exposition during the "Oceans Unmoving" arc... and he does it so poorly most characters consider it a form of torture.
Exposition in Sluggy is natural as breathing to the characters. They don't think anything is wrong with it happens.
Old-Riff in the 4U City Red arc spouts exposition for weeks.
Red Mage usually does this in 8-Bit Theater, although Thief took the role when the Light Warriors were in Elfland.
Rainer from MSF High is this, combined with being a Handsome Lech. He's getting more and more lampshade hanging.
Various characters from Eon's Comic have filled this role, but SSTV News anchor, Charlene Mc Faire is by far the most prominent example; indeed, her sole purpose has been to provide exposition on plot developments, either in the form of a recap or a condensed way of informing the readers of government decisions. Often no one in the story is even watching the news!
The current storyline in The Inexplicable Adventures of Bob! is set on an alien planet. Hence, the cast's resident alien, Princess Voltuptua, has doled out an awful lot of exposition to the humans (and the audience) lately.
Agneta: Welcome to another sunny day on Mars... our delightful planet. Raymond: So it looks like we don't know what planet we're living on, Agneta? Agneta: For all I know, you may have become idiots overnight.
Before those, there was Nannasprite, who filled both John and the audience in on things like "why meteors?"
This is lampshaded relentlessly in DM of the Rings, a LOTR parody, in which Gandalf is made to be Mr Exposition in every way, even more than he is in the books and films. He is even referred to as Mr Exposition on a number of occasions.
In Questionable Content, Momo fills this role in regards to the history of AIs in the QC universe. Jeph clearly has some pretty clear ideas about the universe, and Momo is often used to share them with the audience.
In the Whateley Universe, a lot of the teams at Whateley Academy seem to have them. Ferret of the Good Ol' Boyz, Stopwatch of the Masterminds, Foxfire of the Whitman Literary Girls (well, it's not really a superhero team).
This makes sense, because Ferret is the information-finder and inventor for his team, while Stopwatch is the information-collector and inventor and obsessive control-freak leader of his team. Foxfire has the problem that several members of her group are much bigger expositors than she is, so she has to cut them off just to get in her own exposition.
And Phase, for Team Kimba. If there's an answer to be given, especially in a class, you cannot shut him up.
Gubaru from the web fiction serial Dimension Heroes, while serving a purpose as mentor and part-protector of the multiverse, serves the majority of the series as an exposition machine.
Played with in zOMG!; the expositional character who mysteriously disappears at the beginning is actually The Dragon. He reappears near the end of the game to provide more exposition, this time in the form of Just Between You and Me.
Hans Krebs, the Wehrmacht general in the Youtube Downfall Parodies, although he leaves the really bad news for Jodl to announce.
Any and all contributors to TV Tropes Wiki. You could just watch these shows to see the tropes in action. But no, you want someone to explain them to you.
The Global Guardians PBEM Universe has a villainous example: The Hermit of Tarot has the power to see patterns of cause and effect. By studying literally anything, he can detect the patterns involved and predict what will happen next with almost pinpoint certainty. The Emperor has him study the stock market, news reports, the weather, and pretty much every other type of continually-updated information in order to predict world trends and to explain past events. This makes him Tarot's own personal Mr. Exposition.
Eric in TV Tropes Will Ruin Your Life serves as this in the second episode by simultaneously warning James and explaining to the audience what will happen to him over the course of the story.
Doctor Insano serves as this at the end of To Boldly Flee to explain what happened to the Plot Hole and give a heartwarming speech. When Film Brain expressed incredulity that Insano came all the way there just for a plot dump, he admits he was really there to hold them up and get the stuff they stole back.
In both his appearances, Frostbite ends up explaining the current item/dilemma in order to advance the plot. He doesn't do much outside of expositions after, despite his combat-savvy skills.
At times, Sam Manson often covers this ground, too.
Jérémie Belpois of Code Lyoko often ends up in this role, with generous heaping of As You Know and Technobabble. The two-part prequel, "XANA Awakens", even starts with him registering a video diary of how he discovered the Supercomputer.
Summer Gleeson in Batman The Animated Series. Justified as she's a news reporter and she's usually shown on a TV screen, where she's supposed to be addressing the Fourth Wall. This is not an Idiot Lecture: there must be quite a few people in her audience who are interested, else her ratings would tank and the station would have her doing something else.
Dib on Invader Zim — or at least, Zim must think he is, since he goes into Exposition Mode when pretending to be Dib.
Lampshaded in Spongebob Squarepants where a glowing "Exposition!" sign appears over Spongebob's head when he says "And look! Mr. Krabs is back from his vacation!"
Peter: I walked into the kitchen and sat down at the table. I looked with a grimace at the questionable meal Lois had placed in front of me. Of course I'd never tell her how disgusted I was with her cooking, but somehow I think she knew. Lois had always been full of energy and life, but lately I had begun to grow more aware of her aging. The bright, exuberant eyes that I had fallen in love with were now beginning to grow dull and listless with the long fatigue of a weary life. [Lois knocks Peter out; hours pass] I woke several hours later in a daze.
Nox, the Big Bad in season 1, provides plenty of exposition... mostly by soliloquizing. Or through his own "clockwork puppet show". Which is still perfectly in character, considering that he's insane. And damn creepy while doing so.
Ruel Stroud, being the oldest and most well-travelled of the Five-Man Band, otherwise fulfill this role for the heroes about the various places they visit or people they meet. And he's doing it mostly for free!
Parodied in the South Park episode "Asspen" when Stan is challenged to a ski race down the K-13.
Teen:(steps into frame) The K-13? But that's the most dangerous run in all of America. (steps out of frame)
The above quote is from a lampshading of this trope in Freakazoid!, when Freakazoid notes that his mentor Roddy has a lot of lines in this episode, Roddy goes into a rant about being... well, Mr. Exposition.
In WordGirl, there is a nameless character with the sole purpose of alerting the heroine of criminal misdeeds in other parts of town. (He is usually looking for the police station and just so happens to stumble across mild mannered Becky Botsford. The fandom refers to him lovingly as Exposition Guy.
Star Trek The Animated Series episode "How Sharper Than A Serpent's Tooth". The sole function of Ensign Walking Bear is to provide background information on the ancient cultures he's an expert on.
Zecora the zebra in My Little Pony: Friendship Is Magic sometimes acts like this. Whenever something strange happens and none of the ponies in Ponyville know what to do, not even Twilight Sparkle, Zecora is often the one to tell the Mane Cast what's going on.
In Mortal Kombat The Journey Begins, Raiden spends much of his time explaining the backstories of both the tournament and their future opponents. Justified in that as a god he is ineligible to enter the tournament directly.