Long Runner Cast Turnover
The cast a work started with looks very little like the cast it ends with
(Trivia) Hail to the Long Runner, the show that stands the test of time. But not all Long Runners pass that test unscathed. Actors die, or get fired, or lose a contract dispute, or retire, or simply don't want to play the same role for the rest of their foreseeable career. But creators and executives don't want to let their Cash Cow Franchise or treasured premise go so easily. Alternately, often the inverse is true, and shows often become Long Runners due to allowing cast turn over. So the show continues with replacement cast members...and so occasionally you get shows where the show's main cast hardly resembles the original. Nearly all of the above can apply to characters in Literature and other works without human actors, if the series spans enough time In-Universe and/or has a high turnover. To qualify for this, a significant percentage of the work's main cast, including recurring, named supporting cast, has to change. Red Shirts, extras and guest stars don't count. A one man show only needs the one person to change, but that won't cut it for an Ensemble Cast. However, deciding what percentage is "significant" would amount to drawing an arbitrary line in the sand for no good reason, so take it to discussion for a judgment call if you're not sure. Having a lot of turnover is by itself a neutral phenomenon, but for many people, it's a cause to believe a show has Jumped the Shark, is Ruined Forever or is a Franchise Zombie, especially if the departing cast were a main reason for the show's appeal to them.
- Since the original CSI Crime Scene Investigation premiered in 2000, its later seasons have seen the departure of three of its leads (Grissom, retired, and Catherine, new job, and Ray Langston (who replaced Grissom), forcibly resigned), two of its secondary leads (Sara, quit from PTSD but now Commuting on a Bus, and Warrick, Killed Off for Real) and a number of its recurring supporting roles (Wendy, Sofia, and the very short tenure of Riley, meant to replace Sara). Most of the departures were of the "actor wanting to move on" variety, but contract disputes and in Warrik's case, personal problems, also factored.
- Doctor Who of course invented The Nth Doctor in order to survive 40-plus years but also rotates though a long list of the Doctor's companions; the show's time travel premise makes it fairly easy to write old companions out and new ones in.
- ER transplanted most of its original cast over the fifteen seasons; while some (Susan Lewis) came back and then went away again, and some of the characters came back in the final season, the final cast was composed of none of the members of the original cast. This even gets lampshaded in the final season. One of the new characters meets one of the original characters and they realize that the staff of the hospital changed so much over the years that they have no common acquaintances. All the people who worked in the hospital when the original character left already stopped working there by the time the new character arrived.
- Series/Law & Order ended with a completely different cast than when it started. The series lost its last original cast member at the end of its tenth season, when Steven Hill's Adam Schiff retired. So half of its run was done with no one from the first season cast. The Other Wiki has an entire section dedicated to the cast/character changes and overlaps.
- M*A*S*H had a significant cast turnover during its eleven seasons. Alan Alda (Hawkeye), Loretta Swit (Margaret), and William Christopher (Father Mulcahy) were the only main cast present for the entire run. Jamie Farr (Klinger) was also present for the entire run of the show, but he started off as an extra. The military hospital setting made it easy to write characters in and out with the excuse of them getting drafted, transferred, and discharged.
- Mystery Science Theater 3000 lasted long enough to see every actor walk away for personal reasons. It began as a Mad Scientist and his assistant tormenting a janitor and his robots, but eventually ended as a megalomaniacal woman, a Doctor Zaius expy, and a brain guy tormenting an erstwhile temp worker and... well, the same robots, but with different voices. Joel, the creator and main host character, left the show to Mike in the middle of season five, neatly dividing the series (and fans) into two eras. Both hosts went on to start their own movie-mocking franchises in Cinematic Titanic and RiffTrax. Both of those shows feature a mutually exclusive subset of MST3K's cast (except for Mary Jo Pehl, who has appeared in both series).
- Only three regulars of Night Court made it all the way through the show's nine-year run: Harry Anderson as Judge Harry Stone, Richard Moll as Bull the bailiff, and John Larroquette as prosecutor Dan Fielding. Three different actresses filled the role of the second bailiff (as different characters). Karen Austin, who played the court clerk and was Judge Stone's original love interest, left before the first season was over and was eventually replaced by Charles Robinson as Mac. Four different actresses played public defenders--Gail Strickland in the pilot, Paula Kelly for the rest of Season 1, Ellen Foley for Season 2, and Markie Post for Seasons 3-9.
- New Zealand-produced soap opera Shortland Street first aired in 1992, and as of 2011 only one of the original cast members remains (Dr Chris Warner).
- Spooks went through a very large number of cast changes in its run. Only one character, Harry Pearce, appears in all ten seasons and every other position in Section D had at least three different occupants over the show's run.
- Stargate SG-1, almost. Despite three members of the original Four-Man Band making it to the series cancellation (one of them having spent a year dead for tax purposes), most of the surrounding cast and all of the big bads were gone two seasons earlier. Only Walter remained unchanged.
- NBC's Late Night block has gone through this a bunch of times:
- The Tonight Show has gone through at least five different hosts, all of whom brought in their own people to run the show in a new direction. The only exception may be when Jay Leno was brought back to the show in 2011.
- Late Night has gone through a similar situation but with only three hosts - four if you count its predecessor, Tomorrow with Tom Snyder.
- Later: First it was a one on one private interview on a simple set between Bob Costas and another person. After Costas left it became Later with Greg Kinnear with a live audience. A series of rotating guest hosts each brought their own sensibilities to the show. Now it's Later with Carson Daly which is completely different than any of the others.
Hello, Unknown Troper. You'll need to get known to lend a hand here.