Even though it was not a sitcom, Lassie was able to have a long run even with the multiple changes in direction of the show.

As for sitcoms. The Doris Day Show seemed to have a yearly change of direction and still last for a few years.

What other shows lasted longer than a season after a major overhaul?

Going back into the early 60s, the Joey Bishop Show was totally retooled after the first season.

In the mid 60s Hazel was revamped for the fifth and final season.

I feel Dennis the Menace changed when George Wilson (Joey Kearn) passed. Maratha Wilson (Sylvia Field) left. No Freemont. Dennis was getting too old for his Character.

Going back into the early 60s, the Joey Bishop Show was totally retooled after the first season.

In the mid 60s Hazel was revamped for the fifth and final season.

Yeah I think with both there were network changes. Bishop went to CBS and back to black and white which was really odd. I wish the show kept the first season format. With Hazel it switched networks and the cast change pretty much ended it I think. But wasn't Shirley Booth talked into the additional season?

I feel Dennis the Menace changed when George Wilson (Joey Kearn) passed. Maratha Wilson (Sylvia Field) left. No Freemont. Dennis was getting too old for his Character.

I agree and think the last season was a stretch considering Dennis was no longer an accidental trouble maker.

Maybe MASH fits into this. It went from straight comedy to social commentary with humor thrown in.

Petticoat Junction also had some alterations more for casting than flat out format changes. The focus on music towards the end of the series was a bit much for me.

A behind the scenes change, but Seinfeld was still strong without Larry David

Wonder Woman

Saved By The Bell(Original): Lisa, Zack & Screech are attending Bayside with Kelly, Jessie & Slater

Newhart: Leslie & Kirk were respectably replaced by Stephanie & Michael

Yeah I think with both there were network changes. Bishop went to CBS and back to black and white which was really odd. I wish the show kept the first season format. With Hazel it switched networks and the cast change pretty much ended it I think. But wasn't Shirley Booth talked into the additional season?

Joey Bishop was one of the oddest situations in the 60s. It started on NBC for season 1 in black and white, with two or three episodes produced in color. The show was completely revamped for season 2 on NBC, and was produced in color; season 3 on NBC followed. For the 1964 4th season it switched networks to CBS, and returned to black and white.

Yeah I think with both there were network changes. Bishop went to CBS and back to black and white which was really odd. I wish the show kept the first season format. With Hazel it switched networks and the cast change pretty much ended it I think. But wasn't Shirley Booth talked into the additional season?

I probably need to research the Hazel situation. NBC cancelled Hazel after the fourth season, and CBS picked it up, with the caveat that the lead actors needed to be re-cast to younger actors. Screen Gems complied, and wrote in a move for Hazel to George's brother's home, and wrote out Don DeFore and Whitney Blake.

I think the ratings weren't stellar, but good enough to be picked up for a sixth season. However Shirley Booth ended it due to declining health.

Like I said, some of this may be off--I'm going on memory alone.

Barney Miller had quite few changes over the years. Home scenes with Liz were dropped early on. Chano and Fish departed, Dietrich and Levitt were added. Yamaha (jack Soo) died.

A Different World first season with Lisa Bonet, Second season - Fifth with Jasmine Guy Kadeem Hardison, then Sixth season with a w hole brand new cast

Friday Night Lights let the entire first group of kids graduate and brought in a whole new cast. I've never seen anything like it - and it worked.