Nowadays, of course, that’s just by way of a placeholder until some advertiser makes an attractive offer for product placement. 
The characters get accidentally trapped in a basement or supply room or something all night and have to really communicate.
I’ve seen that one used in at least half a dozen shows.
Likewise with: The episode opens en medeas res – the aftermath of a fire or robbery or other disaster – and one character walks in and all the others on the scene each tell their side of the story in flashbacks and in the most self-aggrandizing way possible. I even saw that done once on Magnum PI which was not strictly speaking a sticome.
Alternatively, there’s also the inexperienced teenager or father doing a load of laundry, and either shrinking a sweater to a comically small size, or having the load of whites come out pink due to some bright red object being in the same load.
Of course, 80% of all sitcom weddings are called off at the last minute, at least half of these at the “speak now or forever hold your peace” point.
If the overweight husband has to go on a diet his dinner will consist of a lettuce leaf and a carrot stick. Smaller portions do not exist in sitcom land.
The ol’ Rashomon chestnut. Dozens of examples of this one.
How the the “accidental answering machine message”? Character A says something terrible on another’s machine. Spends rest of episode attempting wacky ways to retrieve it.
Or the ol’ “Half the cast is on vacation.” Hang a few minutes of new footage around flashbacks to previous episodes. I think 80% of all TV shows in history have done this one.
A character overhearing and misinterpreting something would cover about 80% of all the plotlines on “Three’s Company”.
two characters in two very different but fairly urgent situations end up talking to each other and each assumes the other one knows their situation. They end up having a conversation where they’re both talking about two different things but they don’t realize it.
concussions. Concussions are the best because it’s one of those TV-serious things that someone can recover from whenever it’s convenient, but you get the “OMG SHE’S UNCONSCIOUS! IS SHE DEAD?” moment and, if you like, some hallucinations or amnesia or something.
The sports episode. Either the office softball team has to play against the rival office, or there’s some episode where the dad/mom/uncle coaches the kid’s team… and either screws it all up by cheating/obviously favoring the kid, or teaches the kid and the team to be good sports. A lot of times, the kid with glasses and asthma and leg braces and dyslexia and cancer and syphilis gets a home run/winning goal for his dead blind mother.
Along those lines, the hidden talent/hobby. One of the characters suddenly has a talent or hobby that is central to the episode but never mentioned again. Like the kid enters an art contest and everyone’s all “of course you’ll win! you’re the best artist in the school!” and the kid has never, and will never again, talk about art.
and along THOSE lines, there always seems to be some episode where someone has started a band. And the main-est character is always the lead singer.
And along those lines, the main set of characters are front and center in every activity, cool and geeky: sports, singing, yearbook, the drama club (cliche #bazillion, when the two kids in the play have to kiss)…I’m talking to you, “Saved By The Bell”.
This scenario is often used as a lead-in for the inevitable “clip show” episode when writers get lazy or do not have the time to beat the deadline and instead rely on putting together excerpts from past shows (as the characters reminisce upon their recent past) to build a new episode.
I think Mad About You may have been the worst. First they had the “locked in the bathroom and forced to communicate” ep where their bathroom was the size of an airplane hangar. Then it was “we’re having a baby” and they realized they needed to use their storage room as the nursery. A storage room! They had this whole bedroom-sized room just for storage, like you’d pay for a 2BR instead of a 1 BR just to load up and close off one room???
/aside, sorry
Just as the exception that proves the rule…the funniest single sitcom scene of the past 20 years (MHO, of course) was the Drew Carey episode where they form a band, and Kate wants to be the lead singer.
Yes, but when the Three Stooges were brewing beer in the bathtub and it turned out they ALL added the yeast? Comedy gold.
And it got Bobby London fired from the Popeye strip- some storyline about the Seahag mishearing about Olive wanting to get rid of a baby doll and believing she was getting an abortion. Now that’s comedy!
I suspect (although I’m not certain) that this is not because of writers getting lazy, but because of network executives wanting to save money by producing an episode in which much less actual new material is filmed. Filming new material being expensive, what with having to pay writers, cast, gaffers, etc.
And, in real life, my father’s done both. More than once.
Ah, I can’t believe no one has mentioned this one (though pregnancy was mentioned):
When someone is giving birth, she has to do one or both of the following:
- Boldly declare that she doesn’t want any pain medication, since she wants the birth to be natural; then when the pain hits, she loudly cries, “I want the drugs!”
- When in the throes of birthing pain, she must either physically assault her husband, who is holding her hand; or, at the very least, she must scream at him, “You did this to me! I hate you!”
How about the “We were really, really, really progressive back in the day” rule? Whenever a sitcom is set in a specific past time period, and all the regular characters exhibit the most modern, up-to-date PC attitudes & beliefs. Examples -
Happy Days - Richie befriends a black kid and invites him to a party at the Cunningham house, which rankles everybody in town EXCEPT Mr. & Mrs. C., Joanie, Chachi, Ralph & Potsie, Richie’s g.f. (forget her name) and even blue-collar, high-school dropout tough guy ‘the Fonz’, who are all open & accepting toward Richie’s friend, despite the harshly segregated time period. (The black kid is never seen again though.)
M.A.S.H. - A patient confesses to Hawkeye & Trapper that he was wounded by members of his own unit, because they’d caught him ‘in the act’ with another man. Both doctors are perfectly understanding & sympathetic toward him, even though during that time period homosexuality was considered a mental disorder.
That 70s Show - It’s the late 70s, the very era of Roe vs. Wade. Teenaged meathead Kelso gets a feminist-leaning, book-smart, college-bound girl pregnant… and no-one, not even self-proclaimed feminist Donna ever mentions the possibility that she might have an abortion. A late-70s era young feminist gives up college to have Michael Kelso’s child??
Yeah, “accidentally”.
The people trapped in basement/log cabin in snow/elevator etc. scenario often has the revelation at the end that they weren’t actually trapped. The car engine was working, the lock just needed to be rattled a bit to open and the like.