Like your namesake? 
Oh one more:
A guy will go in for a new job and meet his new boss- a woman…wow! (Very sitcommy if said guy was making fun of this woman before. And the audience goes “Whooooooooo!!!” and claps when it is revealed that the woman he taunted before is his superior.)
How about, “the rubber raft scenario”
I first saw this on an episode of “I Married Joan” which was produced in the early 50s – and since Joan Davis recycled all her old vaudville material, it had to be around long before that.
The setup: Character A does something that annoys character B, promises to stop, but keeps doing it. As test/punishment, character B sets up an elaborate (and visually hilarious) trap, like sending an inflatable rubber raft through the mail when wifey is always opening his stuff.
Character A must go through elaborate efforts to hide or repair the trap, but is soon discovered and forgiven in time for the final fadeout.
Studio Audience: AAAAAWWWWW!
Excellent list! Another one, submitted by my wife:
Man struggles mightily to open pickle jar (or other physical task, such as lift a heavy object) while woman stands by talking to him. This struggle goes on for a while until the woman gets frustrated and opens the jar (or lifts the object, etc.) with ease, causing the man much embarrassment.
The sitcom cliche that always makes me change the channel is the “character makes a blunder that will get him/her in minor trouble, so instead of fessing up like a mature adult, character continues to build an escalating house of cards built of increasingly implausible lies, until character is finally completely screwed.” Actually, now that I think of it, that’s about fifty percent of all sitcom scripts.
Ah! This one goes back at least as far as the 1930s, being the lead-in to one of the greatest scenes in any P.G. Wodehouse novel: the drunken speech at the grammar school.
In RIGHT HO, JEEVES, Gussie Fink-Nottle, the teetotaler who is infatuated with the study of newts, is roped into handing out prizes to the boys at the Market Snodsbury Grammar School. He is terrified of public speaking, so Bertie Wooster (and about six other characters) decide to provide a little Dutch courage by spiking his orange-juice bottle with gin. In addition, Gussie decides that now’s the time to finally try a little alcohol, and, having no prior experience, knocks back half a decanter of brandy.
Touched on in the Perfect Strangers posting, I find most sitcoms/movies these days seem to be based around one character having some important fact they need to share, but the other characters won’t listen until it’s too late, or they butt in and say something that makes the first character not want to share.
Sally: Here comes Jim now. I’ll tell him about my transgender operation, and maybe he’ll understand.
Jim: Hello Sally. How are you, my sweet?
Sally: Jim (nervous), I have something I have to…
Jim: Sally, before you say anything, I must tell you that you are the most beautiful woman alive. Speaking of women, on the way home, I saw a cross dresser. Can you think of anything more sick?!
Sally: Err, well, I…
Jim: Now, what were you saying?
Sally: I… umm… I wanted to know what you thought of my new dress!
(Canned Laughter)
This is frustratingly common in sitcoms - especially the Nanny!! 
So many good cliches here. All the ones I thought of have been mentioned already. The only thought left is why doesn’t anyone ever lock their door?
Oh wait. One more scenario. The budding romance, like in Who’s the Boss, or Moonlighting.
Hah, I caught you trying to fool us, Ike. I saw a special on the History Channel that said there was no TV back in the thirties. And if there was no TV then there couldn’t have been any comedy. Back then everybody just ran around fighting Nazis and dinosaurs and stuff.
If any two characters enter an elevator or walk-in freezer they will inevitably be trapped. The same thing will happen if anyone plays with handcuffs. What key?
Yeah those thirties stegasauruses were treach. :rolleyes:
But I digress. What about the running gag? (eg., "We were on a break! in “Friends.”)
Yay first person on the new page!!
I never saw “I Married Joan” but I remember this same storyline from a “Dick Van Dyke” episode.
If a pregnant woman gets on an elevator, the elevator will get stuck and the woman will go into labor, without fail.
A character is a big fan of a celebrity. Strangely enough, this has not previously been mentioned before, but is established in the first minutes of the episode. Then, coincidentally, we learn that the celebrity is about to appear at a local PTA beneift. The character will do anything to meet the celebrity, who is, of course, played by himself or herself. Wacky antics follow. Popular with writers because they don’t have do write as much dialogue for these episodes, as the audience will wildly cheer for about five minutes every time the special guest star comes on the set.
If there is a big party, or an important dinner with the spouse’s employer, the character doing the cooking will burn everything, switch sugar and salt, or otherwise destroy the meal. Wacky antics follow.
A love letter or hate letter is accidentally mailed. The character who wrote the letter NEVER meant for it to be mailed, but simply left it laying around in an addressed envelope. Wacky antics follow as the characters try to prevent it from actually reaching the recipient. Variation: hate letter is mailed, then character realizes it was “all a big misunderstanding”. Wacky antics follow as the characters try to prevent it from actually reaching the recipient.
Character is visiting wealthy boss, neighbor, or in-laws. Character engages in some harmless and amusing snooping when the host is the other room. Character reaches into a precious vase, and gets his hand stuck in it! Wacky antics follow as the character must now strike nonchalant poses while his hand is stuck in a vase.
A neat site for those people who are in a love/hate relationship with sitcoms is http://www.jumptheshark.com
My first “multi-pager”!
The granddaddy of them all: A woman, in the process of giving birth, with either
a. shout out, “I want drugs!” when it was decided ahead of time that she would not use painkillers when in labor
or
b. grab the father of the child and yell, “You did this to me!” or some variation thereof. THIS CLICHE WILL ALWAYS OCCUR, WITHOUT FAIL, WHEN THERE IS A PREGNANCY IN A SITCOM!!
The Lenny and Squiggy Entrance:
Laverne - “Who would be stupid enough to do that?”
::Door bursts open to the sound of Lenny’s trademark - “Hello!”
Audience erupts in howling laughter!
Meant to hit preview, but missed it!
Let me throw out another show that did this a lot to jog some memories: Night Court. I distinctly remember the “Giving Birth in the Elevator” episode. But what made it really witty was the guy stuck in the elevator with them worried about his leather shoes. Bwahahahaha.
I get tired of the cross-dressing men gag.
Seems like every episode of some shows has it in one form or another.
It’s as tired as Benny Hill.
if someone on the show is doing baking for a baking contest, a charity bazaar, or to make some extra cash, they will lose a piece of jewellry somewhere in the baked goods
the husband will never remember the wife’s birthday or their wedding anniversary
the children in the show are smarter than the adults
anyone entering flowers in a flower show (or starting a garden) will include a plant that will be mistaken for marijuana by other cast members, who then destroy the garden or flower arrangement
*already mentioned in the thread, but bears repeating for continuity
**MY presents never look like that. Did they have a professional wrapper? Oh, props department did it.
***and just WHERE did they go shopping at oh-dark-thirty? The 7-11? And getting the ‘perfect’ (read: expensive) present for each person.
Mistaken presents - male neighbor/co-worker asks main character to hide an expensive piece of jewelry or fur coat, bought for neighbor’s/co-worker’s wife as a surprise. Main character’s wife finds now-hidden expensive gift, and thinks it’s from main character, expressing deep love (and possibility of sex that evening). Main character must find way of getting expensive present back from wife without 1) hurting her feelings and 2) letting neighbor/co-worker know of mix-up. Hilarity ensues, especially when main character’s wife finds out expensive present is for [insert dramatic music]…‘another woman’.
Hi Opal!