Shows that ended their runs with most of the original cast gone

[RetroGuy2000]

You Can't Do That On Television - Only Les Lye playing the producer of the show remained for the full run. All the original kids were eventually replaced.

[swany13]

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Originally Posted by RetroGuy2000

You Can't Do That On Television - Only Les Lye playing the producer of the show remained for the full run. All the original kids were eventually replaced.

Speaking of Nickelodeon sketch shows, Josh Server was the only original cast member of All That to remain during its entire first run/first six seasons (1994-2000).

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Originally Posted by Christopher

Melrose Place. All but two main cast members left Melrose Place at the end of season 5 so they brought in all these newbies in season 6 to help fill the void. It didn't work since FOX had to pull the show in the middle of the season and burn off the episodes with a final season the next year. Not even Heather Locklear could save that train wreck. Melrose Place proved if you're going to lose all of your cast in one season after being on for quite a while, just end the show. No new character can replace an established character fans grew to like for so many years.

Saved By The Bell The New Class. Only Belding lasted the entire series run. None of the kids from season 1 lasted long.

Once Upon A Time had a reboot in their last season with only two of the original cast members from the first season. Still it wasn't that bad though. I was expecting worst.

The Lucy Show had only Lucy that stayed the entire six seasons. Viv and the kids left at the end of season 3.

Melrose Place's parent show, Beverly Hills, 90210 ended its run in 2000, with only Kelly, Steve, Donna, and David being there from the beginning a decade prior. All of the Walshes (the last being Brandon) were long gone by that point. And Kelly was for all intents and purposes, the defacto lead character (she had already replaced Brenda as the female lead for many years leading up to that point) given that Jennie Garth became the first billed star after Jason Priestley departed.

I'm kind of surprised that Hazel hasn't been mentioned yet as Don DeFore and Whitney Blake were infamously dropped upon the show's move to CBS for its final season. This left Shirley Booth and Bobby Buntrock as the only original cast members left.

[stevea]

Yes, on the mention of My Three Sons in a previous post, after 12 seasons only Fred MacMurray and Stanley Livingston were left.

Similar situation with another old show, Make Room for Daddy/Danny Thomas Show. After 11 seasons and 7 or 8 different apartments, only Danny Thomas and Rusty Hamer remained standing.

[Reinhold_Weege]

Night Court only had three original cast members last from the series premiere to the series finale: Harry Anderson, Richard Moll and John Larroquette.

[AKA]

ER, which was on for 15 seasons, lost its final original cast member (Noah Wyle) at the end of season 11. Every original cast member from season one guest-starred at least once during the final season, though.

First season cast (1994-1995), in order of exit:
Sherry Stringfield (left season 3)
George Clooney (left season 5)
Julianna Margulies (left season 6)
Eriq LaSalle (left season 8)
Anthony Edwards (left season 8)
Noah Wyle (left season 11)

Sherry Stringfield did return during season 8, only to leave again at the beginning of season 12.

15th and final season cast (2008-2009), in order of joining:
Parminder Nagra (joined season 10)
Linda Cardellini (joined season 10)
Scott Grimes (joined season 12, recurring seasons 10-11)
John Stamos (joined season 13, recurring season 12)
David Lyons (joined season 15, recurring season 14)
Angela Bassett (joined season 15)

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Charlie's Angels ended with only Jaclyn Smith and David Doyle still being around from the first season. Cheryl Ladd is the second longest tenured cast member, but she came in the second season after her on-screen sister, Farrah Fawcett left. If you want to count daytime soap operas, then The Bold and the Beautiful, which debuted in 1987, has Katherine Kelly Lang (Brooke Logan) and John McCook (Eric Forrester) to still be on the show today.

It's a Living ended its run in 1989 with only Barrie Youngfellow, Gail Edwards, Marian Mercer, and Paul Kreppel to still being on the show dating back to its debut on ABC in 1980. Another network to syndicated '80s sitcom, Charles in Charge only had Scott Baio and Willie Aimes to be on all five seasons.