Inspired by this thread about TV shows that have turned over all or most of their original cast, I got to thinking about the opposite extreme.
All 6 of the main actors in Friends appeared in all 238 episodes; no additions or subtractions to the principal cast throughout the show’s run.
Are there any other ensemble shows that lasted as long, and nobody missed even a single episode?
I found an answer to my own question, at least according to IMDB, which credits the 5 principal cast members of Frasier with 263 episodes each. (Though I wonder if somebody can verify that – not a single episode without Roz or Daphne?)
Any others?
Seinfeld (173 episodes per IMDB)? The Simpsons (440 episodes per IMDB) voice actors?
You could argue for The Simpsons, as all 4 of the Simpsons plus Harry Shearer have done all 440 eps, but you could also argue that Hank Azaria counts as part of the main cast, and he has missed a few. Also, Maggie Roswell, who voiced Maude Flanders and a number of other characters, left the show a few years back.
As for Seinfeld, Julia Louis-Dreyfus was not in the pilot, and Michael Richards was not in the Chinese Restaurant episode. Though all 4 of the main cast did last through every season, so I suppose they belong in the conversation.
I Love Lucy has the same four during its entire run. Ethel and Fred seems to have missed a couple of episodes, but they were still part of the cast the entire time.
The Dick Van Dyck Show had Van Dyke, Mary Tyler Moore, Rose Marie, and Morey Amsterdam as the main cast the entire run (as well as Larry Matthews, who often didn’t appear), though some episodes didn’t feature Rose Marie or Amsterdam, even though they were credited.
Perry Mason had the same cast from start to finish, though, again, some actors may not have been in all the episodes even though they were credited.
Get Smart only listed Don Adams and Barbara Feldon in the opening credits; they appeared in all shows. Edward Platt (Chief) didn’t appear in every show, but was only listed in the end credits.
How about “Dragnet” (1951-1959)?
Jack Webb was in all 276 episodes as well as the opening and closing announcers, George Fenneman and Hal Gibney.
And there was “The Mod Squad”, all 4 principals were in all 123 eps. (Michael Cole, Peggy Lipton, Clarence Williams III, and Tige Andrews).
And I guess I’m just showing off my age, but I remember “The New People”, a 1969 blockbuster series which had all 6 principals in all 17 incredible episodes! 
“Perry Mason” ran from 1957-1966. Raymond Burr, Barbara Hale and William Hopper and William Talman stayed the whole way. But…
Ray Collins, aka Lieutenant Tragg, had intermittent health problems and missed a lof of episodes. He died in 1965, before the show’s final season. When Collins was sick, Lieutenant Anderson (Wesley Lau) was used in his place. When Collins died, he was replaced full-time by Richard “Oscar Goldman” Anderson, who played Lieutenant Drumm.
I’m almost certain that Daphne missed a few episodes when she “went to the fat farm” (i.e. Jane Leeves had a baby).
Say what you want about David Schwimmer, but I think you can credit him for this. Very early on he urged the all the Friends to agree to the same salary. They each got the same raise. This made them a single unit without any resentment that So and So was making more (I think this is what happened to Three’s Company, John Ritter was making more than the women) and thus Warner Bros/NBC couldn’t get rid of one or more of the cast due to a salary dispute, or bring in someone’s little cousin on the cheap.
According to IMDb, none of the top five cast members of “Emergency!” (Randolph Mantooth, Kevin Tighe, Julie London, Bobby Troup and Robert Fuller) missed more than an episode or two for the show’s 7 seasons. The three main firefighters (Tim Donnelly, Marco Lopez and Mike Stoker) only missed a handful each.
The Brady Bunch? Oh, and definitely Gilligan’s Island! : )
The IMDB listing for **The Beverly Hillbillies **shows that all four members of the Clampett family were there for every one of the show’s 274 episodes. However, Mr. Drysdale and Miss Jane each missed about 20 episodes during the 9-season run. But technically, those two weren’t listed as co-stars until a season or two after the beginning. So you can count it either way.
And speaking of The Dick Van Dyke Show, Ann Morgan Guilbert, who played Millie, once said she was offered a regular role, but she turned it down, because, having 7th billing, she would have made less per episode than she did as a non-regular. Likewise, Martin Landau was always a “special guest star” on Mission Impossible.
Also, the original voice of Moe and Mr. Burns, Chris Collins, left after the first season. (Roswell was always credited as a supporting cast member- the four main members of the Simpson family, Shearer, and Azaria are the ones who get top billing.)
Only for the first season; he was a regular cast member in the second and third seasons, and then was gone altogether when the fourth season started.
This is one of the flaws of the setup of the IMDB; it’s very bad at determining who were regulars on many shows from the 50s. In many of their entries for obscure 50s and 60s show, they don’t list any of the main cast on the main page for the show.
Dragnet had plenty of turnover as Joe Friday’s sidekick: Barton Yarborough played it in the pilot but died of a heart attack after the series started running. Next came Barney Philips as Ed Jacobs, followed by Herb Ellis as Frank Smith. Ellis was replaced in the role by Ben Alexander (long before the two Darrins). And, of course, this doesn’t include Harry Morgan in the revival.
BTW, the OP asks about shows that retained their original cast, not those where all cast members appeared in all episodes.
The main cast of Leave it to Beaver was on the show the entire run. Same for The Bob Newhart Show
Lost in Space?
I mentioned both scenarios in the OP… It started out as a question about having the same regular cast throughout all of a show’s seasons, then I kind of sidetracked myself when I found the tidbit about all the Friends being in all the episodes. So the discussion is open to either; I’m running a pretty easy-going thread here. 
In the Bradys’ case, keeping a cast of 9 on board for 5 seasons is pretty impressive. I know Robert Reed was written out of a couple of episodes in the final year due to his ongoing feud with Sherwood Schwartz. Schwartz later said that if the show had been picked up for another season, Mike Brady would have been killed in a plane crash over the summer. I think he meant it.
Interesting that on IMDB (which I know is not an infallible source), only Carol, Alice, and Greg are credited with being in every episode; everyone else shows one or two fewer. And for Gilligan’s Island; Ginger, Mary Ann, and the Professor have one fewer episode listed than the other four.
I can’t recall ever seeing a BB without all 6 kids or a GI without all 7 castaways… am I wrong or is IMDB?
Unless you count the reunion TV-movies, in which Tina Louise did not appear.
Talman was there in the beginning and in the end, but he missed quite a few episodes in the middle while dealing with his own legal problems.
Hell, even Hopper and Hale missed quite a few:
Wheelz said:
For Gilligan’s Island, imdb is not wrong. They are, however, counting the original pilot “Marooned” that did not air until 1992. In that premiere, Ginger was played by Kit Smythe, the Professor by John Gabriel, and there is no Maryanne, but a girl named “Bunny”, played by Nancy McCarthy.
http://www.imdb.com/title/tt0588101/
Brady Bunch, doing a spot check, I find that Maureen McCormick was not in Season 2 Episode 11, What Goes Up?
I did this by comparing her episode list against Florence Henderson’s. A similar comparison could be done for the other cast members to determine which episodes they were not in. I leave this as an exercise for the reader.