I know other characters have been killed off shows before, but was this the 1st and only time a character was killed off who was the leading star of the show?

http://t0.gstatic.com/images?q=tbn:ANd9GcT-l-9QgIvvwPBdUL484B5v5NH-03lNr0F0tOoRY0zn1BQeY0ql

This may be debatable, but when Jean Hagen didn't want to continue on "Make Room for Daddy" after 1956 and quit the show, Danny Thomas literally killed off Margaret Williams' character at the start of the 1956-57 season, allowing him to woo and eventually win the heart of Kathy Williams, a/k/a Marjorie Lord. The show continued and thrived after their marriage as "The Danny Thomas Show."

I also ink the death of Valerie Hogan character was a rare example of a show's title character being killed off? (Which resulted in the show's renaming from Valerie to The Hogan Family.) Any other examples of TV shows' title characters being killed off?

Susan Saint James was one of the title characters on McMillan & Wife. She left in a contract dispute and her character was killed off (and the show was retitled).

Diana Hyland was the female lead on “Eight is Enough”. She passed away in real life and her character was killed off.

Kathy Nolan was the female lead on “The Real McCoys”. She left in a contract dispute and her character was killed off.

I found this on the MSN Entertainment page in an article about Sara Gilbert addressing the cancelling of the "Roseanne" show.

At the end of the article they included A Related Slideshow: 5 Ways “Roseanne” could continue without Roseanne Barr – Before I even started to read further about it I was thinking that reminds me of “Valerie” continuing without Valerie Harper. But I was still surprised when I got to the number 4 out of the 5 ways... and this is what I saw...

THE CONNERS

If Valerie Harper’s Valerie — a 1986 sitcom about a working mother raising three boys — could transition into The Hogan Family after losing its star to behind-the-scenes disputes, why can’t Roseanne continue in the same fashion? There are plenty of Conners to go around (the table).