When a sitcom producer finds something that works, the bit tends to be recycled anytime an episode needs a lift. Think Niles Crane and physical humor, Rob and Laura Petrie doing a song and dance, Klinger walking through post-op in a dress, or Phoebe’s songs at the coffee house.
What are some other sitcoms with famous bits? – preferably ones that are actually funny.
“Norm!”
Norm Peterson’s Famous Quotes
(from TV’s “Cheers”)
“Can I draw you a beer, Norm ?”
“No, I know what they look like. Just pour me one.”
“How’s a beer sound, Norm?”
“I dunno. I usually finish them before they get a word in.”
“What’s shaking, Norm?”
“All four cheeks and a couple of chins.”
“What would you say to a nice beer, Normie?”
“Going Down?”
“What’s new, Normie?”
“Terrorists, Sam. They’ve taken over my stomach and they’re demanding beer.”
“What’ll it be, Normie?”
“Just the usual Coach. I’ll have a froth of beer and a snorkel.”
“What would you say to a beer, Normie?”
“Daddy wuvs you.”
“What’d you like, Normie?”
“A reason to live. Give me another beer.”
“What’ll you have, Normie?”
“Well, I’m in a gambling mood Sammy. I’ll take a glass of whatever comes out of that tap.”
“Looks like beer, Norm.”
“Call me Mister Lucky.”
“What’d you say, Norm?”
“Any cheap, tawdry thing that will get me a beer.”
“What would you say to a beer, Norm?”
“Hiya, sailor. New in town?”
(Coming in from the rain)
“Evening everybody.”
Everybody: “Norm!”
“Still pouring, Norm?”
“That’s funny, I was about to ask you the same thing.”
“Whaddya say, Norm?”
“Well, I never met a beer I didn’t drink.”
“Hey Norm, how’s the world been treating you?”
“Like a baby treats a diaper.”
“Would you like a beer Mr… Peterson?”
“No, I’d like a dead cat in a glass.”
“How’s life treating you?”
“It’s not, Sammy, but you can.”
“What’s the story, Mr. Peterson?”
“The Bobbsey twins go to the brewery. Let’s cut to the happy ending.”
“Hey Mr. Peterson, there’s a cold one waiting for you.”
“I know, if she calls, I’m not here.”
“Beer, Norm?”
“Have I gotten that predictable? Good.”
“What’s going on, Mr. Peterson?”
“A flashing sign in my gut that says, ‘Insert beer here.’”
“Hey Mr. Peterson, Jack Frost nipping at your nose?”
“Yep, now let’s get Joe Beer nipping at my liver, huh?”
“What’s going on, Mr. Peterson?”
“Another layer for the winter, Wood.”
“Whatcha up to, Norm?”
“My ideal weight if I were eleven feet tall.”
“How’s it going Mr. Peterson?”
“Poor.”
“I’m sorry to hear that.”
“No, I mean pour.”
“How’s life treating you, Norm?”
“Like it caught me sleeping with its wife.”
“Women. Can’t live with 'em … pass the beer nuts.”
“What’s going down, Normie?”
“My butt cheeks on that bar stool.”
“Pour you a beer, Mr. Peterson?”
“Alright, but stop me at one…make that one-thirty.”
“How’s it going Mr. Peterson?”
“It’s a dog eat dog world, Woody and I’m wearing Milk Bone underwear.
“What’s the story, Norm?”
“Boy meets beer. Boy drinks beer. Boy meets another beer.”
“How’s about a beer, Norm?”
“That’s that amber sudsy stuff, right? I’ve heard good things about it!”
“What’s going on, Mr. Peterson?”
“The question is, `what’s going ‘in’ Mr. Peterson?” A beer, please, Woody.”
“Can I pour you a beer, Mr. Peterson?”
“A little early isn’t it, Woody?”
“For a beer?” “No, for stupid questions.”
Not showing Maris. Initially they weren’t planning on having her never be seen but as the writers kept making her sound more and more outlandish, they realized they could never cast her and so she stayed faceless.
I’m not sure if that really counts, though. Hmm. Oh well.
The Beverly Hillbillies recycled the same bit, over and over again
Jethro and his 6th grade education
Jethro and his career ambitions, double naught spies, brain surgeon.
Elly and her animals
Granny and Mrs Drysdale Feud
Granny and her white lightning
Mr Drysdale being cheap.
Elly needing a fellow
How many different names did Endora call Darrin on Bewitched. How many times did a spell on Darrin backfire on Endora or Serena?
“Close the door!!!” - Murphy Brown
Not to mention the ongoing secretary gag.
Little known fact… this exact quote (except for the names, of course) was used between William Powell and Myrna Loy in “The Thin Man.” The bit probably predates that movie too, though.
Actually, come to think of it, the old “little known fact” bit was frequently used on Cheers, too!..TRM
As long as we’re talking about Cheers, Norm’s wife Vera’s face was never shown either. She did show up in one episode–with a cream pie covering her face to preserve the mystery!
Any character: “Did you ever hear of anything so stupid in your whole life?”
<enter Lenny & Squiggy>
Lenny & Squiggy: “Hellooooo!”
“This is Carlton your doorman . . .”
THE Greatest recurring sitcom gag has got to be the Carlton Dance from The Fresh Prince of Bel-Air.
A great sight gag that was used sparingly yet judiciously and one that never failed to deliver.
Here’s one of Alfonso Ribeiro’s variations on the theme. A winner every time.
Did someone say dance? That brings me to the Arrested Development chicken dances, which in turn opens up the Arrested Development floodgates. That show had enough recurring gags to fill ten threads alone.
The unseen character is a well-worn sitcom trope. See also Wilson Wilson, Carlton (Your Doorman), Enid Kelso, and Rob Petrie’s secretary Marge.
On Will & Grace:
On Golden Girls:
Bewitched:
Mrs. Kravitz: “Hey Abner, there’s something weird going on across the street at the Stephens’es house.”
Abner: “Take your medicine, Gladys.”
Or just the whole "Endora puts a wacky spell on Darren just before he’s trying to land a Very Important Account. Thanks to the account, Samantha thinks up a brilliant idea that Darren pitches to the clients - guaranteeing that McMann & Tate get the account.
Three’s Company: Someone overhearing something and misunderstanding it, with ridiculous results.
ETA: Speaking of ridiculous, Perfect Strangers: Don’t be ridiculous.
All In The Family-
“Heeeere’s your beer, Archie!”
“You are a meathead!”
“Stifle yourself!”
Archie saying something mildly offensive, then Mike goes on a long rant, then Archie says something really offensive, which Mike just rolls his eyes at.
Archie doesn’t want Edith to do something because she’s a dingbat. Edith does it anyway, and Archie gets mad. Edith proves her opinion/input is valid, which Archie grudgingly accepts.
Newhart: I’m Larry, this is my brother Daryl, and this is my other brother Daryl.
The recurring gag was the parade of outlandish excuses Niles reported to explain her absences. I’d love to see a list of those 
Another recurring gag on Murphy Brown was her house in a constant state of being repainted.
A few from Seinfeld:
Kramer throwing open the door and bursting into Jerry’s apartment
Helloooooo…Newwwwman
Joe Sacamano
Get OUT!!! (accompanied by Elaine pushing someone in the chest)
George Steinbrenner
IIRC, there was one episode where the show’s characters all thought she was there, but it turned out to just be a coathanger.