Already Met Everyone

""With a good Sequel, you can expand the universe, introduce new characters, explore more of the existing ones, take what we know and push it in radical new directions. With a Prequel, all that imagination is devoted to devising ways to shoehorn the existing characters into the old story, to pretend they all knew each other back then. The universe gets smaller as we find out that every page of history contains the same dozen names.""

- David Wong on the Star Wars prequels.

As a series progresses, it has a lot of events in it which are supposed to be happening for the first time. Once you do more of the series, you can have characters who have met before meet again, or you can revisit old locations or plots, or whatever.

But if you're doing a Prequel, the temptation is to write the same way, by using elements of the series that are familiar to you and your audience. This means using varying degrees of Retcon to say that the "first" appearance of someone or something wasn't really the first, so that you can use it in the Prequel. In extreme cases this can lead to a Continuity Snarl where most of a story's cast, antagonists, abilities, etc. all showed up before the main story even began.

Sometimes the pre-first first appearance gets explained away by giving characters amnesia or otherwise effectively wiping out the event, which can itself get weird if it happens lots of times.

A variation may be seen when Time Travel gets involved, and characters meet people in the past who aren't supposed to know them until later. This can be solved either by Laser-Guided Amnesia, or by having the other characters not recognize the time traveler (because he/she either has changed his/her appearance or meets them so far in the past that they've forgotten it by the time they meet in the present).

See also Spinoff Babies, Everyone Went to School Together, Everyone Is Related, Early-Bird Cameo and Forgotten First Meeting.

Anime and Manga

 * The 2002 Lupin III television special "Episode 0: First Contact" tells the story of how all the main characters met, all at the same time. This contradicts previous origin stories that showed Lupin and Jigen being old friends, then meeting Fujiko, and then meeting Goemon much later. However, the whole thing is told through the Framing Device of Jigen being interviewed by a news reporter, and it's never confirmed that the events of the movie really happened.
 * Apart from Lupin producing the MacGuffin of the movie during the epilogue.

Comic Books

 * Back in the Silver Age, the Superboy series pioneered this, with just about everything from Superman showing up "first" in Superboy, including most notably Lex Luthor being a former childhood frenemy.
 * It also provided at least one serviceable subversion, creating Lana Lang to stand in for Lois Lane rather than importing Lois into his childhood. She even became fleshed out into her own character. Pete Ross arguably was a stand in for Jimmy Olsen and even he took on his own life (being Superboy's first Secret Keeper aside from his parents, both from an in-continuity and real world perspective.) Although in the end, Superboy met both Teenage Lois and Infant Jimmy anyway.
 * He also met Aquaman, Batman and Green Arrow.
 * As the G.I. Joe comics progressed, it ended up that Snake-Eyes had met practically everyone else in the franchise prior to joining the Joes, from fellow Joes Stalker and General Hawk to the villains Cobra Commander (whose brother was responsible for the death of his family), Destro, Baroness and Storm Shadow.
 * Apocalypse from X-Men was later revealed to have ecountered, over the course of his long life, the following characters from different corners of the Marvel Universe: Mister Sinister, Externals, Avengers villain Kang The Conqueror, the Brood, Acient Avatar of Khonshu, Abraham van Helsing, Jonathan Harker and Dracula.
 * Wolverine was later retconned to have meet loads of different characters in the past, including Captain America (comics), Peter Parker's parents, Black Widow, Mystique, Nick Fury, Incredible Hercules, Daredevil enemy Nuke, not to mention basically everybody ever tied to Weapon X. In fact, revelation about Weapon Plus does this to Weapon X, revealing it's ties to Nuke and Project: Rebith, that created Captain America.

Film

 * In the movie Young Sherlock Holmes, not only do Holmes and Watson know each other in boarding school as young teens rather than meeting as adults as happens in the books, but in a short post-credits scene it's revealed that Moriarty's enmity towards Sherlock Holmes goes much further back than the books indicate: he was a junior master at the school that both Holmes and Watson went to, and the mastermind of the first case Holmes ever solved. Lestrade also plays a part.
 * The writer also interestingly makes Holmes and Watson the same age. From internal evidence in other stories in the Holmes canon, Holmes in A Study in Scarlet is 27 and Watson 31, so not likely to be bunkmates.
 * The Dragonball Z movie Dead Zone has the characters meet Gohan for the first time. Ironically, even though it takes place after Dragonball and before the Dragonball Z series actually began (IE: With Goku and Piccolo's battle with Raditz), the main characters don't even know Gohan exists in the very first episode of DBZ.
 * We were expecting Anakin to have met Obi-Wan and Yoda in the Star Wars prequels. Not so much C-3PO and R2-D2.
 * C-3PO had his memory wiped at the end of Episode three.
 * According to the Pokémon 4 Ever movie,  first met Ash, Misty, Brock AND Team Rocket 40 years previously when   was brought forward in time by Celebi. Of course, none of the main cast make the connection due to age differences. But you'd think he would have mentioned it at some point.
 * 4Kids actually went out of their way to make it completely and utterly obvious that, to the point where there were extra scenes added solely for the dub. The original was much more subtle in that it was basically one scene during the credits, specially.
 * 4Kids actually went out of their way to make it completely and utterly obvious that, to the point where there were extra scenes added solely for the dub. The original was much more subtle in that it was basically one scene during the credits, specially.

Literature

 * Dragonlance is like this. You have the Chronicles, then the Twins trilogy, and then they start filling in every character's backstory, usually featuring one or more characters from the chronologically later canon. Considering that the characters were supposedly no more than fourth level or so when they started the 1st Edition AD&D module, Dragons of Hope, the likelihood of them having that many glamorous adventures together is... pretty small.
 * Artemis Fowl did the Time Travel version in The Time Paradox.

Live Action Television

 * Smallville has had appearances (sometimes even as regulars) of Luthor, Brainiac, Bizarro, Toyman, an In Name Only version of Mxyzptlk, Doomsday, Darkseid, Supergirl, Lois Lane, Jimmy Olsen, the Daily Planet, the Fortess of Solitude, the Phantom Zone, several DC superheroes, and pretty much everything else associated with Superman even though the entire premise of the series is about Clark's life before being Superman. Suffice to say, the pretense of being a Prequel to the Superman mythos was dropped some time ago.
 * Yeah, although Lois specifically showed up a little early, there is some forgiveness in that this show lasted ten years and essentially transitioned to a straight-forward Superman show, minus the costume.
 * James Kirk was the "first person" to do lots of stuff. But it turns out Jonathan Archer did them all firster.
 * Disney prequels are especially terrible about this:
 * The Hercules TV series has Herc being quite The Hero, even though much later, in the movie, he admits he's never done anything heroic to the disenchanted citizens of Thebes. He spent far more time causing accidents, and never went to Thebes in the series (usually in Athens, but went almost everywhere else in or near Greece besides Thebes). There's the fact that up until his reappearance as an adult in the movie, Hades didn't even know he existed, in fact he thought he had been killed as a baby.
 * At the very least though, in the one episode Megara appeared, they hurriedly had both she and Hercules lose memory of each other so that they could meet again in the movie.
 * Babylon 5 example: the Prequel TV movie establishes that John Sheridan had already met and been on a mission with Dr Stephen Franklin during the Minbari War, some twelve or thirteen years before Sheridan became Franklin's commanding officer. In all fairness, when Sheridan joins the show his first scene with Franklin is a serious professional talk and doesn't indicate whether or not they already knew each other.
 * But when Dr. Franklin met Marcus Cole for the first time the latter one had to explain the meaning of the word Izil'zha to him. I'm pretty sure I'd never ever forget a single word if it saved my life when my death was almost certain.
 * Happened a lot on Friends, thanks to the various flashback episodes the show featured during its ten year run. In particular, Rachel and Chandler met at least three different times.
 * As did Felix and Oscar of The Odd Couple.
 * Tripped over in Sledge Hammer. Since the first season ended with everyone dying in a nuclear fireball, the second season was a prequel to the first season—despite the fact that the main characters met in the first episode, and weren't partners before.
 * An alternative interpretation is that there was a 5 year gap between the penultimate and final episodes of the first season, and season 2 fitted in there. This seems to be what the 'disclaimer' at the start of season 2 is implying.
 * Community established in "Foosball and Nocturnal Vigilantism" that Jeffrey and Shirley met for the first time when they were 12 - but it wasn't until this episode that they realized it. While it was a very memorable experience, it was also very traumatic for both of them and resulted in major personality shifts for both of them. In effect they are very different people than when they briefly met as kids.

Theater

 * Wicked. Prior to The Wizard of Oz, the witch Elphaba knows Glinda, met the Cowardly Lion, in the musical knows the Scarecrow and Tin Man, and of course who she also has met.

Video Games
"Max: Funny, though. All this time we've spent talking to the COPS, and you never once mentioned you're the guy who built Bluster Blaster. Sam: Just never seemed relevant, I guess."
 * In one of the later episodes of of the recent Sam and Max Freelance Police game series, it's revealed that Sam built Bluster Blaster, an arcade game he met earlier in the series and showed no signs of recognising, when he was a preteen. Of course Sam and Max lampshade this:


 * In Silent Hill Origins, the prequel to Silent Hill 1, the only unique characters to the game are Travis, his family, and the Butcher.
 * Averted in Professor Layton and the Last Specter. It's the fourth game in the series, but set first in the timeline. However, it still features appearances by Granny Riddleton, Inspector Chelmy and Barton, who chronologically first meet the Professor later. To avoid plotholes, the Professor and Luke never cross paths with them, only Emmy does (she never appeared in the earlier games). In fact, Granny Riddleton quickly goes on vacation and leaves her cat behind to perform her usual job, so the Professor never sees her.
 * Metal Gear Solid managed to retroactively pull this. Metal Gear Solid 3: Snake Eater almost completely averted it - Ocelot was the only character from later in the timeline to show up. Metal Gear Solid 4: Guns of the Patriots, however, retconned it so everyone of importance from all the games (including 3) turned out to be deeply involved in the Gambit Pileup.

Web Comics

 * Parodied in PvP when the main characters were brought back in time by a magical d20 and stumbled across Skull. When they get back, they ask him why he never mentioned meeting them before. He says he "used to drink a lot back then".

Western Animation

 * Spoofed repeatedly on Futurama, which features Scruffy the Janitor, a fellow who meets the cast for the first time... every time he appears. Whenever Scruffy enters a scene, there's usually a mention of how he has no idea who any of the main characters are, and none of them know who he is, either, thus deliberately contradicting all his prior appearances. This leads to such lines as "Gee, I've never seen Bender so upset... or ever before."
 * The second movie plays with the spoof when it reveals that
 * A Simpsons flashback episode showed that Homer and Marge had briefly met and shared their first kiss as children, but due to Marge's straight brown hair and Homer's Elvis Jagger Abdul-Jabbar's patch over an injured eye, didn't recognize each other when they attended high school together.
 * One flashback episode shows Homer meeting Ned Flanders while Marge was pregnant with Lisa. A later flashback episode shows Homer and Marge meeting Ned and Maude while both couples were childless.
 * As with Futurama, spoofed in the early years with Mr. Burns. In his very first appearance, he tells Homer, "Ah, Simpson, at last we meet." Was true at the time, but a couple of later flashback episodes showed that he had already met Homer twice before at least. Of course, this was all part of a then-Running Gag that Burns could never remember who Homer was and had to be corrected.