Most sitcoms i've watched tend to follow a specific pattern in storytelling. There is a main story (A) involving the principle character(s) and a side story (B) which is interesting but generally unimportant to story A or to the overall story arch of the show (if it even has one).

Why do sitcoms generally adhere this format? What purpose is B supposed to fill? Why does it work so well?

Additionally, are there any other possible structures that a sitcom can have? Examples of alternative structures would be nice.

  • I'd say the B-story is filler they use to pad out the amount of time the A-story falls short of the episode runtime, but that may just be my cynicism. Dec 8, 2014 at 22:37
  • 2
    I'd say it's mostly for providing diversification so that the A story line doesn't get boring. It's especially interesting when both storylines suddenly intertwine. Afterall most sitcoms show a group of more people or a particular microcosmos (family, clique, company, ...) rather than a single portagonist experiencing adventures on his own. So it's natural that others have going on interesting things, too, and storyline B is to hint at that. Yet, with more than two storylines the casual sitcom viewer would be overstrained. But that just as a thought, I don't have an actual idea so much either.
    – Napoleon Wilson
    Dec 8, 2014 at 22:54
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    To give the entire cast "something to do" or "some lines to say" In a sitcom the entire cast is generally used every episode, but using all of them in every episode, as part of main story line A would be ... hard. So relegate a chosen "supporting cast" for that episode. TBBT does this often. The entire main cast gets paid whether or not they are used, per episode, not per line. Compare this with an ensemble-cast type drama (such as Southland) where only those cast members who are used for that episode are given lines. Some cast may not even be given screen time at all. (is my theory anyway)
    – CGCampbell
    Dec 9, 2014 at 0:24
  • Interestingly The Simpsons nearly always starts with 2 or 3 minutes of a "B" or "red herring" story then switches to the main "A" story, the "B"/"red herring" story not referred to anymore in the rest of the episode. It's so consistent it feels like an exercise the writers deliberately do in order to try and force themselves to be original.
    – T. Rutter
    Dec 17, 2014 at 12:14
  • It has occurred to me that Seinfeld regularly used the A-B-C structure and it was done in a half hour. I am wondering if this was done in earlier shows. Apr 30, 2017 at 13:16

1 Answer 1


The purpose of the “B” story or subplot is so that the supporting characters in the program have something to do in addition to providing reactions to and validation for the actions of the protagonist. The B story/subplot interweaves with the main story and often provides the main story with added measure of heft that it may lack to to editing and the need to get the episode filmed.

if you watch sitcoms from early American television, subplots were rarely used and the weakness of the main stories became readily apparent. The action was concentrated around the protagonist(s) and, if the story wasn’t particularly enthralling, the discriminating viewer might find that episode to be boring and they might tune away or remember that episode as not being one of the “better” ones. With a subplot, you can retain the interest of the viewer by providing them with a number of story elements, you keep the cast happy as all of the supporting actors have distinct roles within the series and you keep the writers happy as they demonstrate their creativity and potentially expand the underlying legend of of the series.

A different format is the A-B-C format, where an additional subplot is added; however this usually occurs on special hourlong episodes or when the series has been on for a number of seasons, Another variation is the “A Christmas Carol/It’s a WOnderful Life type of episode where the protagonist is shown how their life intersects with those of the supporting cast in way which they are unaware. This is a “cheat” as it allows the entire episode to be about the protagonist without appearing to actually be that way.

  • Your answer sounds plausible, but do you have any sources to back up your claims; academic, industrial or otherwise verifiable?
    – Paul
    Dec 16, 2014 at 18:49
  • thewritersguide.co.uk/sitcom.html
    – Mistah Mix
    Dec 16, 2014 at 18:51
  • @MistahMix The link seems to be broken.
    – mattiav27
    Apr 30, 2017 at 13:33

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