Well, like I said earlier. It was “The Smoking Room”. They only used one set. Whether it’s obscure or lost in time…
The British sitcom The Royle Family was mostly contained to the titular family’s living room. The show was also mostly filmed from one angle as well, that of the family TV. Most of the cast thus staring directly into the camera.
As did Marion and Geoff with Rob Brydon
Sorry, but just going from memory I can think of more than 30 other sets The Honeymooners used:
[ol]
[li]Outside the front of the apartment when Ralph & Alice get kicked out[/li][li]Outside the front of the apartment when they’re sneaking away on the fishing trip[/li][li]Outside the front of the apartment when they’re going to get Ralph’s driving award[/li][li]The pool hall when Ralph witnesses the bank robbery[/li][li]The pool hall when Ralph picks a fight with Harvey’s little friend[/li][li]The gym where Ralph meets Harvey[/li][li]Ralph’s boss’ office when he’s impressing his old friend[/li][li]The restaurant they all go to at the end of that same episode[/li][li]Norton’s apartment when Ralph thinks he’s hiding from his mother-in-law[/li][li]Norton’s apartment when Ralph makes the recording to send to Alice[/li][li]Norton’s apartment’s bedroom when Norton is sleepwalking[/li][li]The raccoon lodge for the raccoon election[/li][li]The raccoon lodge for the costume party[/li][li]The Raccoon lodge for his brother-in-law’s bachelor party[/li][li]The street above Norton’s manhole when Ralph meets him for lunch[/li][li]The lawyer’s office when Ralph thinks his inheriting $40 million[/li][li]The employment office when Ralph hires a maid[/li][li]The IRS office when Ralph forgets to sign his return[/li][li]Ralph’s boss’ office when he makes him try Alice’s appetizer that’s really dog food[/li][li]The City Pound when Ralph brings back the dog[/li][li]Ralph’s boss’ mansion when he tries to teach him pool[/li][li]The train sleeper car when Norton handcuffs them together[/li][li]The TV studio when Ralph goes on The $99,000 Question[/li][li]The TV studio when Ralph & Norton do the commercial for the kitchen multi-tool[/li][li]The hospital when Ralph thinks Norton is hurt[/li][li]The apartment basement when Ralph becomes the superintendent[/li][li]The plush apartment of Ralph’s supervisor they go to with the dim-witted sexy trophy wife[/li][li]The opening scene in the gangster’s hideout where they’re making the counterfeit money[/li][li]The magazine office when Ralph sells them the story thinking he’s going to die[/li][li]The street where he gives the newspaper reporter his ‘King of the Castle’ routine[/li][li]The bus drivers’ lounge where he calls Alice to run right home and make dinner from the same episode[/li][/ol]
These were all in just the ‘Classic 39’ original episodes (watched them repeatedly in syndication as a kid). Barney Miller had much fewer in eight seasons*!*
Ralph and Norton also went to a Racoon convention, taking the train there. At the convention they happened to run into big TV stars Jackie Gleason and Art Carney. Sadly due to confusion Norton never got to meet Carney, and Ralph never got to meet Gleason. I may be wrong, but I think it’s the episode where Norton asked “Do you mind if I smoke?” and Ralph responded “I don’t car if you burn!”.
I don’t remember it ever being out of the store per se but there are also lots of scenes in the lunch room, so even if we are only counting frequent locations, it is a three location sitcom once you include the office. Then there are infrequent or once-used locations like other floors or even the roof.
Not a tv show per say but 12 angry men.
The Hulu original show Booth at the End takes place entirely in a single restaurant booth. They did change to a different restaurant between seasons 1 and 2 though.
And yeah, Jeopardy, Jerry Springer and Jimmy Fallon’s shows all take place in the same location. But I’m assuming the OP meant “fictional shows”.
Did they ever leave the ship in either Red Dwarf or MSTK3?
The winner has to be “St. Elsewhere,” since { SPOILER ALERT }all the action took place inside young Tommy’s head. 
Ha! You win! 
In Red Dwarf, at least, they often found excuses to leave the ship and land on planetoids or visit another ship or travel through time to Earth or similar.
MST3K, at least several times over the seasons, NOT including scenes DEEP 13 or The Ape Planet/Roman Times/Camping Planet arcs, nor Castle Forrester, nor the Hex-Viewer vistors.
There was Mike’s trial for destroying those three planets, and the walk thru the “bucolic glade” during the wormhole episode, to start.
Does the final scene in Mike & the Bots efficiency studio apartment after they crash count?
AYBS had at least one scene in a theatre, maybe two? One where the staff end up in a “blue movie” theatre (when they filmed the store commercial, and ended up previewing it in that theatre but with no video, only sound IIRC), and another when Miss Brahms demonstrated her “making out” skills (that she learned on the streets of Catford) on Mr Humphries…
Even by sitcom standards Friends used a lot of sets; we regularly saw three apartments and the coffee shop, and the show was more than rich enough to set scenes elsewhere as need be. I’m hardly a Friends scholar but just from the episodes I’ve seen can think of fifteen other sets, including film sets, the inside of an airplane, and a park where they played football.
WKRP also had a larger number of sets than you might think, while most of the scenes are in the radio station, it’s a medium sized office offering multiple sets; the booth, the reception area, Mr. Carlson’s office, the bullpen, Andy’s office, and they did go external on many occasions; the turkey scene, of course, but a lot of others.
For modern, real-budget sitcoms I think Barney Miller has to be the winner, but Cheers gets some sort of award for doing the most with one set.
Cheers was pretty clever about it also. We saw the backroom and Melville’s occasionally, but mostly we only saw people as they exited and entered those locations.
Them meeting their acting alter-egos must have been from a later special, they didn’t do anything quite that gimmicky in the original run. The “I don’t care if you burn” joke on the train was from #22 I mentioned above (with the handcuffs).
Like many, Barney Miller was my first thought.
Then I thought about it a bit, and remembered:
[ul]
[li]Barney’s apartment[/li][li]Dive hotel with Harris and Dietrich with a witness[/li][li]Wojo’s apartment[/li][li]Barney in jail[/li][li]I guess that’s about it[/li][/ul]
Yeah, this is going to bother me now. I remember them taking the train to the convention in the episode you mention. I’m pretty sure this was before the Gleason show was in color, but having seen most of those in B&W I may have been fooled.
Here it is - Jackie Gleason Show - 1956-57 - Episode 9 - Catch a Star
Alice and Trixie also meet their counterparts. I saw this years later, but before the Honeymooners were revived on videotape in the 80s, probably around 1970.
Was Porridge only set in the jail? The Royle Family didn’t leave the house until Nana died in hospital.