Perfect Strangers: in the pilot, Cousin Larry was Louie Anderson. I haven't seen it, but I think that one speaks for itself.
He was only meant to be a one-off/infrequent character so it stands to reason. He wasn't replaced, though. Heck, at the end of the series they changed Harriet. It most certainly did not get better then.
Fresh Prince of Bel-Air when they replaced Vivian.
Star Trek Voyager: swapping Kes for Seven of Nine
Regardless of the reasons for the change, Jeri Ryan was flat out a better actress and she had some great episodes.
They also cut out Judy Winslow (Jaimee Foxworth) after the 4th season.
Fresh Prince (that had to have been mentioned by now, right?) is a huge one - seems most I see are partial to the original Vivian, but I had no preference. I suppose the show took on a less serious demeanor around the time of the replacement, which of course is likely the reason for it anyway. If it got better would naturally depend on which overall feeling you preferred. I think the zany stories, for me at the time, were more enjoyable. I was in the perfect age range for that though, if I were older I might have felt the other way. I love 'em both though.
They also cut out Judy Winslow (Jaimee Foxworth) after the 4th season.
Replacing Mischa Barton with Autumn Reeser after season 3 of the OC was a good move and the show improved. Same with replacing Christopher Mayer and Byron Cherry with John Schneider and Tom Wopat after season 5 of Dukes of Hazzard was a good move
This is debatable, but Three's Company...
Suzanne Somers left and Pricilla Barnes came in. I always thought Pamela was hotter than Suzanne, so I liked the change.
Not sure if serious because it's so obvious, but this really doesn't count. The stars of the show held out, they replaced them with two imposters, and the network caved when they realized that was a bad idea. The ratings never rebounded (season 6 and 7 were both lower rated than the imposter year) and it was cancelled two years later. I wouldn't say the show got better, it just went back to what it was.
I felt like Jefferson just allowed for so many more interesting/funny storylines. Steve was a little stiff/boring. Jefferson was a more interesting character. But that said, all of the characters evolved so much during those first couple of years that it's almost not a fair comparison. In the beginning Peggy cooked, Al was occasionally nice/happy/complimentary and not as pathetic, Kelly wasn't old enough to be a complete ****, etc. I feel like it took a couple of years for them to really hit their stride.I actually didn't mind Steve, maybe because I watched Married With Children from the first time it aired on FOX. Many people didn't get to see it from the start, it was even not run in certain places at the beginning for being offensive. I remember David Garrison from a Jason Bateman show called "It's Your Move", so I always liked him.
Newhart: Replacing Kirk and Leslie with Michael and Stephanie was a good move. The Leslie character wasn't that interesting, and Julia Duffy was a much better actress. The Kirk character was funny, but was also so mean-spirited that it was impossible to like him. Every sitcom "jerk" character still has to have some redeeming quality, which is also why I preferred Winchester over Frank Burns.
Three's Company: Suzanne Somers and Priscilla Barnes were both fine for the show, but it was the one played the roommate in between them that I couldn't stand. She was clumsy, and that one character trait about her was used in almost every episode.
I agree that Mr. Furley was much better than the Ropers, but you had to feel bad for Norman Fell. He never wanted to leave to do the spin-off, because he knew Three's Company would have a long life in syndication. But he was forced into it; and when the spinoff inevitably failed, there was no room to bring him back on the original show.
This is a fun topic. It was written into to both Lindley's and Fell contract that if the ropers did not last for more then one season or 24 episodes they could come back to three company--The ropers lasted 28 episodes. Bernie West who went from Company to The Ropers were welcome back to the show as a writer however Don Nicholl and Michael Ross, where shocked when Don Notts agreed to do the show. Nicholl passed away shortly after telling Fell he could not come back to the show.
Acording to Ross(who wrote a back on his time in hollywood was that unlike nearly everyone else involved in the show--Notts did not complain about the jokes or that he was brunt of jokes--the comment Ross attributed to Notts was something like "That is how it was with Andy". Notts was a guy who came, did what he was told, took his money and went home. While they did not say it--It sounded like Fell got involved in the writing process and that rubbed some the wrong way
Don Knotts really left a mark on so many people. True professional. His physical comedy and energetic delivery were perfect with the three leads. One of the most memorable sitcom characters ever.
In the William Christopher thread we are talking about how MASH actually got better when some of the original actors left(towards the ends we can all agree it got a but preachy)
Changes they made
McLean Stevenson(Lt Col Blake) for Harry Morgan (potter)
Larry Linville(Burns) for David Ogden Steirs(Winchester)
Wayne Rogers(trapper) For Mike Farrell(BJ HoneyCutt)---Not everyone agree with this--but I like Rogers--but having both him and Alan Alda both chasing woman was a bit much sometimes
Other Shows like NYPD Blue(they changed a lot) but the David Caruso for Jimmy Smits changed the show for the better IMO
Night Court and Cheers were both forced to change due to deaths of cast members--but they got good replacements
what other shows can you think of that got better after changes--most get worse--but some have gotten better