A lot of shows go through major changes in format or characters during their runs. Of those who did such canges after one season, what would you say the ratio is of successes (e.g., The Facts of Life) to failures (or at least shows that soon got canceled, like The Jeff Foxworthy Show)?

I would say that about 90% or more fail if they have to make changes after there first season. The Facts of Life was a rare occurence.

With Mork & Mindy, the producers and the network "tampered" with the show's cast and format after the first season and it's ratings plummeted. It was somewhat saved by December of 1979 but the show continually lost its audience and was canceled after the 1981-1982 season. I have read TJ's episode guide and I can see why the fans were so confused and why many of them stopped watching during and after the second season.

However, considering that the comedy potential of the original premise of the series (Mork adjusting to life on Earth) would have been thoroughly mined and would eventually fade away completely sooner or later had the series stuck to its original format all the way through, the network and the producers were somewhat wise to go in new directions. It was a nice idea on paper but it did not work well in practice.

Charles in Charge went under changes after the first season. since ratings were low and the show was almost cancelled so as we all know they changed the Pembrokes to the Powells. a Drastic improvement if i might say so

"A Different World" made major changes after its first season.

Also worth mentioning is "Newhart" which made minor changes after season one but made major changes after season two.

In both cases comparing the first season to the rest of the series is like watching a different series.

PS: though "A Different World" first season compaired to the rest of the series is a wash. "Newhart" first two seasons were much better than the rest of the series run. They got rid of a funny character Kirk and overexposed the one joke ponny Larry, Darryl, and Darryl. Though I still like the "Bob Newhart" show better than any season of "Newhart".

Newhart improved immensely after season 1.

I enjoy looking for the changes in a show after the pilot episode. Sometimes you'll see a new set (like the Cosby Show) or new characters (Jesse).

Hearts Afire had a lot of changes after it's first season. Most of the cast was let go with the exception of John Ritter, Markie Post, Billy Bob Thornton, and the actors who played the kids. Beth Broderick was kept on as another character for part of season two. Season two had John Hartman moving to his home town and buying the newspaper there.

"Curb Your Enthusiasm" made some pretty major changes after it's first season with Larry and Cheryl moving to a new house,the addition of Wanda and a focus more on Larry's work life than his married life.

PS.Season 3 had Larry,Jeff and Ted buying "Bobo's" Resturant as well as new characters Michael,Hugh (and the other people at the resturant),The Broady's,Oscar (the dog) and more emphysis on the character of Ted!

Hangin With Mr Cooper got rid of Dawn Lewis and added two new castmembers for the second season- in my opinion it got better.

Step by Step got rid of Carol's mom and sister after the first season.

Angie, which was a big mistake, changed from the coffee shop setting to a beauty salon. The coffeeshop episodes was funnier and more entertaining.

The same thing happened to Phyllis. They changed nearly the entire cast and put Phyllis into a different environment that was not funny.

One Day At A Time got rid of Richard Masur after season 1.

Love and War got rid of Susan Dey, bad move, after season 1 for Annie Potts. The show was no good after Dey's firing.

Veronica's Closet got rid of Ronnie's ex-husband and father, replacing them with a new boss and love interest.

"Saved By The Bell" obviously became more succesful after it's "8th grade" season.

Well I just thought of another one. Though it was after season 2 but season 1 was like only 5 or 6 episodes so it is like one season.

"In the House"

That show completely changed after changing networks from NBC to UPN and Debbie Allen left the show.

My Three's Company Spinoff "Gabaldi Bound" went through several changes losing half the cast and bringing in 3 previously recurring characters as regulars plus the premise changed from being about college to being your basic buddy/relationship show.