Round Robin

A Round Robin is a story written collaboratively by a group of authors, each of whom takes a turn writing a chapter or section; the chapters are produced in chronological order, or at least in the order in which they are intended to be read. There is no agreed-upon outline for the overall plot, and the authors are all free to take the story in whatever direction they wish when it is their turn to write a section, without consulting the others, leaving those who follow to deal with the consequences of what they have written. By the same token, each must accept what previous contributors have written.

A classic Round Robin has each person writing multiple parts, repeating the same order of authors each round. Variations include each author writing a single part or the authors writing multiple parts without a pattern to the repetition, perhaps not even producing the same number of parts. Another simple variation is to have the same person write both the first and last parts.

A variant on the Round Robin format restricts the author's knowledge of what has come before. Typically in this variant, each new writer will be given only the immediately preceding chapter, and must extrapolate how things got there. Needless to say, this is done only as an intentional gambit to produce amusingly incoherent results; moreso the shorter each chapter is. This variant reaches its ultimate expression in comic strips where each participant is given only a single panel. This variant is often called "exquisite corpse", after a famous phrase created by this method.

A Round Robin presents a number of obvious storytelling dangers, including Flanderization, Character Derailment, Loads and Loads of Characters, Kudzu Plot, Mood Whiplash, Plot Holes, Retcon, Spot Light Stealing Squad, and worst of all Dead Fic if someone fails to go through their turn. In general, the most major danger of a Round Robin is that each author is more eager to introduce his own characters and subplots and then talk about them than to write about characters introduced previously.

Furthermore, it's hard to give a Round Robin an actual ending, since even when all the plot points are wrapped up, someone will likely reveal that this was all the villain's Evil Plan, or another mega-powerful villain will show up suddenly - all in a desperate try to lenghten the story for at least as many pages; of course, it won't work, since everyone else are tired of the story already, and so the Round Robin will never get a proper ending.

A modern day Round Robin only rarely results in a publishable work. It is more commonly produced for the authors's own amusement. It has also been used in Fanfic.

The Round Robin may be one of The Oldest Ones in The Book, as plots involving a group of people sitting down around a fire (or whatever) to tell a story testify.

TV Tropes itself has one.

Comic Books

 * DC Challenge is a rare comic book example where each issue had a different author except the final one. Each part ended with at least one Cliff Hanger and usually several, which the next writer had to figure out how to resolve.
 * Project Pieces is an attempt to create a publishable comic where each panel is drawn by someone else. Within just a few pages it degenerated into a nonsensical stream-of-consciousness.
 * The She Hulk story The Time of Her Life was a very interesting artistic Round Robin. Each artist drew a two pages from the comic in sequence. it was an excellent example of how things can vary depending on the artist. She-Hulk varied from huge 80s perm to normal 00s hair, from bodybuilder to slender in physique, from normal to vast in bust... Etc etc. If memory serves, there was only one writer, however.
 * Done accidentally to the tune of Epic Fail in Countdown to Final Crisis, because the writers and editors apparently couldn't be bothered to look at the preceding issues to keep track of the continuity. The art reflects this as well, not just in the Art Shift as the thing was handed from one creative team to the next, but in blatant Did Not Do the Research such as the incident where the Pied Piper and Trickster fell out of a futuristic plane at sunset at the end of one issue, only for the beginning of the next issue to depict them falling out of a regular jet in the clear blue afternoon. Methinks the series would have been far more enjoyable if it really had been a giant crack-filled bit of fun on the writers's part.
 * Brand New Day was this for Spider Man with writers changing for each story or even during the same story and one issue even has three writers, one estabilishing main event and then them all dealing with an aftermath from different standpoints.

Fanfic

 * The Anime Addventure (sic) is an entire site devoted to Round Robin-style writing, using a branching tree structure similar to a "Choose Your Own Adventure" book; anyone can join in on any plotline by simply picking an option from the end of the most recent episode and writing an installment about it.
 * CAPOW Anime Prose Original Writing; see the link for more details.
 * The Global Ranma Insanity Thread, a combination round robin and text-based roleplay (with, effectively, everybody acting as the Gamemaster) that started on the rec.arts.anime.misc newsgroup and has since migrated to a mailing list.
 * Improfanfic, which involves signups and deadlines to help keep the story moving along at a reasonable pace; unfortunately, this doesn't always work and many stories have since just ground to a halt after the signups withered away.
 * It was reasonably successful for a few years, enough to have Spin Offs, such as Indie Madnesse, but all these sites faced the same problems.
 * Dark Heart High and Magical Girl Hunters are two examples of Improfanfic series.
 * The Renegades is a Kingdom Hearts fic that has three people writing its chapters in a circular fashion, as well as special excerpts written by all of the authors or a one-off chapter written out of turn, which all eventually connect to the main storyline.
 * Thwomp goes to the Chocolate Factory, shared between three Brits, is a particularly hilarious example. It begins with a Thwomp attempting suicide due to boredom at his job as manager of the titular factory, and just gets weirder from there.
 * The TV movies of Script Fic Calvin and Hobbes The Series are co-written by Swing123 and garfieldodie.

Film

 * Four Rooms is a Round Robin Anthology film by four writer/directors about Ted the Bellhop's terrible New Year's Eve. As the only character in all four segments, Ted's characterization varies wildly Depending On the Writer.

Literature

 * Sorcery and Cecelia combines the Round Robin with the Epistolary Novel.
 * Parodied relentlessly by Mark Twain in Roughing It with a chapter about a literary magazine's serialized novel of this form.
 * Cronicas De UP
 * There is a type of Round Robin used in the 18th century novella Little Women, where most of the characters take 'turns's to tell a long story during a garden party to 'entertain' themselves...
 * Black Trillium was written by Andre Norton, Marion Zimmer Bradley and Julian May in this fashion: each of them wrote chapters about her respective heroine (Kadya, Haramis, and Anigel, accordingly), which were then compiled and edited into a single novel. However, the collaboration proved so stressful for all of them that they continued writing in the same universe independently, effectively creating three different continuities after BT.
 * Atlanta Nights, which was specifically written an enormous, Plot Hole-ridden mess.
 * The Floating Admiral, a Round Robin detective story done by many of the great detective authors of the 1920's and 1930's, with each chapter done by a different author, who had to figure out without hints what needed to be deduced from the previous chapters, with the final chapter requiring real detective skills to figure out how to wrap up the plot.
 * The cruise : a novel of murder and romance was a collaborative effort with many famous (and infamous) British authors including Maeve Binchy.
 * Behind the Screen is a short story written by several mystery fiction writers, including Agatha Christie, Dorothy L. Sayers and Hugh Walpole.
 * Much of the Star Wars Expanded Universe works out to be this, but with entire books and even trilogies; there are many writers who often go in completely different directions.
 * The Bantam Era actually defied this trope to an extent. Authors usually stayed on for the entire series, and many were standalone novels. Legacy of the Force suffers from this in a huge way, partly because it was nine books, essentially three trilogies, and all three authors were writing independently at the same time. So, there would be stuff in Book 1 directly contradicted in Book 2. Naturally, pet characters were abound, but rarely saw a huge role in the other two authors's work
 * Naked Came The Manatee, by thirteen of Florida's finest authors, including Carl Hiaasen, Elmore Leonard, and Dave Barry
 * Which is, of course, based off of Naked Came The Stranger, a deliberately bad book created as a collaboration between 24 authors to prove that no matter how terrible the book was, if there was enough sex in it, people would buy it. It became a bestseller in 1969.
 * Dash & Lily's Book of Dares was alternately written by a husband and wife over e-mail. Notably, this fits with the theme within the actual book, seeing as the titular Dash and Lily communicated by writing in the same journal one after the other.

Live Action TV

 * In a way, virtually every TV show ever follows this. After all, the individual episodes in a Story Arc are typically penned by different writers. Examples are obviously too numerous to list.
 * The difference is, most showrunners have a preplanned outline for the season, or perhaps the whole series, which the staff writers must follow. Often the storylines for individual episodes are written by the showrunner or the staff, the credited writer cranks out a draft in teleplay format, and the scripts are then revised once again by the showrunner and staff.
 * The Whose Line Is It Anyway game "Three-Headed Broadway Star" featured the players making up a "hit Broadway love song" Round Robin-style, one word at a time.
 * They had more games like these, for instance the Irish Drinking Song.

Webcomic

 * "El cadaver exquisito" and "El muertito sabrosón" two projects hosted at http://produccionesbalazo.com/, 19 different authors in the both of them, only Spanish but still worth to check.
 * The Centerstorm project, which split off from the old "Fan Art Headquarters" (now a defunct site) Impromanga project; it hosts all of the FAHQ's legacy comics and a number of new titles.
 * The Doji project, inspired by the host site's Monthly Online Manga that gave artists a topic to draw a short comic about each month.
 * The Multi-Artist Exchange improvisational comics, which after some experimentation locked in the artists drawing for each other, and open discussion of where to take the plot is heavily encouraged.
 * The school year starts at WCI High, a collaborative effort by several members of the Webcomics Inc. social network site. The artists have their various characters attend high school together. Normally runs September through May, taking a hiatus during the summer (well, it is high school). Originally stand-alone stories, it started including more and more Crossover events, including the big "Sadie Hawkins Dance" storyline.
 * The site Improfanfic above mentioned was born as an spinoff of another (now disappeared) site named Impromanga.

Web Original

 * The Mad Scientist Wars
 * Draw Your Own Story
 * The Whateley Universe story Parents' Day, which worked out in the end but took about two years to get written. Word of God says they are never going to try that again.
 * In The Nineties, a Round Robin called "Gary and Liz: The Return to Gateway Mansion" was one of the two main features of a website called Kidpub. It was periodically refreshed when it had spiraled out of control, but eventually, everyone just started using it as a time-delayed chat room.
 * There existed a webcomic called Troop 37. The premise was that a boy scout named Jimmy is one morning turned into a teenage girl. A few pages were made by one author, establishing his close friends and family, and then a reader would each call shotgun on drawing the next page of the progressing story of Jimmy's misadventures. The problem was that the artists kept taking a long time to produce the pages. Eventually interest petered out, and the story wound down to an unofficial end.

Western Animation

 * The animated short Anijam consists of segments animated by different animators revolving around a single character. The animators were only given the last frame of the previous segment, which then became the first frame of their segment, and were told only to make sure the character appeared at the beginning and end. The segments range from the humorous to the abstract, and sometimes the character disappears for most of the segment, but reappears at the end for the next one.