A show or movie where the main cast also serve as the writers of the piece. Common in SketchComedy, as well as {{Video Review Show}}s and Internet AbridgedSeries due to their one-man-show nature. The trope can crop up in other types of show as well; it's especially common in {{Sit Com}}s, as sitcom writers often have backgrounds in performance (specifically [[RecordedAndStandUpComedy stand-up]] and/or sketch comedy) and are susceptible to being called upon to act.

When actors get their first writing credit on series they're ''already'' starring in, that's WrittenByCastMember.

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!!Examples:

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[[folder:Film]]
* Creator/MattDamon & Creator/BenAffleck's ''Film/GoodWillHunting''.
* Many of the Creator/JuddApatow-produced films and TV shows, and not just because his films are heavily improvised. Creator/SteveCarell co-wrote ''Film/TheFortyYearOldVirgin'' and Creator/JasonSegel co-wrote ''Film/ForgettingSarahMarshall''.
* ''Film/CasinoRoyale1967'' falls into this category - largely because the actual script was such a mess that producers had to get the cast (who included experience writers such as John Huston, Orson Welles and Woody Allen) to try and make some sense of it. Peter Sellers, the nominal star, also wrote a lot of his own material.
* In Magazine/{{MAD}}'s parody of ''AnimalHouse'', when Dean Wormer threatens the Deltas, one remarks they have more power than he does because some of them are writers of the movie.
* The ''Film/{{Ghostbusters}}'' films were written by Creator/DanAykroyd and Harold Ramis.
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[[folder:Live Action TV]]
* Series creator Rob [=McElhenney=], co-developer Glenn Howerton, and writer Charlie Day all have lead roles on ''ItsAlwaysSunnyInPhiladelphia''. Another co-writer, David Hornsby, plays recurring character Rickety Cricket.
* ''Series/MysteryScienceTheater3000'' cast parts almost entirely out of the production staff, and primarily from the writers, to the extent that [[http://www.mst3kinfo.com/mstfaq/guest.html almost every bit part ever was played by someone who was employed to do something at Best Brains before they appeared on the show]].
** All of the [[TheOtherDarrin replacement actors]] for the main characters ''also'' came from the crew, chiefly the writing staff. It was that kind of show.
* Series/{{Svengoolie}} writes pretty much all his own stuff.
* ''Series/ThirtyRock'' is a show about writers and producers, where Creator/TinaFey plays her own writer/producer character while writing and producing the show.
* A lot of {{Britcom}}s are created and written by the star(s), especially ones who come from a stage or stand-up background:
** ''Series/FawltyTowers'' starred and was written by Creator/JohnCleese and [[CreatorCouple his then-wife]] Connie Booth.
** ''Series/TheMightyBoosh'' is written by its stars, Julian Barratt and Noel Fielding, with [[{{Improv}} additional material]] from Rich Fulcher.
** ''Series/{{Spaced}}'' was created and written by its leads, Creator/SimonPegg and Creator/JessicaHynes.
** Ricky Gervais and Stephen Merchant wrote and starred in ''Series/TheOfficeUK'' and ''Series/{{Extras}}''.
*** ''Series/TheOfficeUS'' also qualifies, as it includes three writers as cast members (Toby, Kelly, and Ryan), and two others have had smaller cameos. Creator/SteveCarell has also written episodes.
* Steve Smith, who portrayed the title character of ''Series/TheRedGreenShow'', also co-wrote every episode. He often worked with Rick Green (who played Bill), and in later seasons, Peter Wildman (Buzz Sherwood) and Bob Bainborough (Dalton) contributed as well.
* Creator/LauraDern and Mike White created and starred in ''Series/{{Enlightened}}'', with White writing ''every'' episode.
* ''TheLeagueOfGentlemen'' has its writing credit read "The Cast and Jeremy Dyson", and it's roughly that literal--beyond crowd scenes and the ''occasional'' woman, you'd be hard-pressed to find a single character not played by series writers Creator/MarkGatiss, Creator/StevePemberton or Creator/ReeceShearsmith.
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[[folder:Sketch Comedy]]
* ''Series/MontyPythonsFlyingCircus''
* ''Series/SaturdayNightLive'', particularly in the first five years (1975-1980) due to the relatively small cast (and especially in the 1979-1980 season, when Creator/LorneMichaels was looking for replacement actors for Creator/DanAykroyd and Creator/JohnBelushi, who left after season four), though the tradition of having ''SNL'' writers as either cast members or bit players continues to this day.
* ''Series/TheKidsInTheHall''
* ''Series/{{SCTV}}''
* Second City, TheGroundlings, and other {{Improv}} troupes generally.
* ''TheState''
* ''Series/TheGoodies'': two of the three main performers wrote it.
* ''Series/AtLastThe1948Show'': four of the five main performers wrote it.
* ''Series/ThatMitchellAndWebbLook''
* ''Series/TheArmstrongAndMillerShow''
* ''Series/LittleBritain''
* ''Series/TheCatherineTateShow''
* ''Series/AlmostLive''
* ''Series/MrShow''
* ''Music/LesLuthiers''
* ''Radio/HelloCheeky'': three of the four main performers wrote it.
* ''Radio Active'' was so full of writers that Helen Atkinson-Wood was the only one who didn't chip in on that front.
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[[folder:Web Video]]
* Pretty much anything on ''Website/ThatGuyWithTheGlasses''.
* ''WebVideo/TheOtherSide'' is written primarily by the actors who play Colorado, Virginia and Turk, the three central characters.
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[[folder:Video Games]]
* ''PuzzleClubhouse'' has a lot of this -- it's a series of episodic games created on a fast-paced schedule (a new game releases on the first of each month), and having all the voice actors on site makes for faster iteration and development. The majority of characters are voiced by Schell Games developers (who also write the episodes, design the games, create the artwork, etc).
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[[folder:Western Animation]]
* ''WesternAnimation/TheVentureBrothers'' has a lot of this: writer/creators Jackson Publick and Doc Hammer spend a lot of time [[TalkingToHimself talking to themselves]]; between them they voice something like twelve characters.
* Same thing with ''WesternAnimation/SouthPark'', but more so. Trey Parker and Matt Stone voice pretty much anyone who's not Chef or a woman (though Trey Parker voiced Ms. Choksondik, as well as a one-time female character -- the S'mores Schnapps lady -- in "The Red Badge of Gayness." Creator/MaryKayBergman was meant to voice her, but had to be replaced following her death).
* Bill Scott, co-creator and head writer of ''WesternAnimation/RockyAndBullwinkle'', shouldered the burden of roughly half the lead voice cast, playing Bullwinkle, Mr. Peabody, and Dudley Do-Right, among others.
* Creator/SethMacFarlane and Alex Borstein both write and perform for ''WesternAnimation/FamilyGuy''.
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