10 Biggest TV Cast Changes Ever

It's risky business for a hit TV show to lose a star and try to stay popular. It remains to be seen how well Ashton Kutcher does on "Two And A Half Men," but here is a look at 10 big cast changes and how they fared.

Slideshow: Stars Who Quit Hit TV Shows

1. Jimmy Smits for David Caruso (NYPD Blue). Caruso famously bailed after one season, and Smits hit a home run as his replacement.

2. Kirstie Alley for Shelley Long (Cheers). Long left in a dispute, and Alley joined Woody Harrelson as a cast member. The show got even bigger.

3. Bill Murray for Chevy Chase (Saturday Night Live). Chase also split after season one. Murray became a huge hit while Chase faded away.

4. Mike Farrell for Wayne Rogers (M*A*S*H). Rogers left and eventually did his own show for CBS. Farrell became a mainstay on the show.

5. Harry Morgan for McLean Stevenson M*A*S*H). Stevenson jumped to NBC to do a sitcom based on the life of Larry King. Morgan became Col. Potter.

6. Jenilee Harrison for Suzanne Somers (Three’s Company). A disaster for all involved. The show hired Priscilla Barnes and let John Ritter carry the sitcom.

7. Brian Dunkleman for no one (American Idol). Dunkelman left Idol after season one and gave the stage to Ryan Seacrest.

8. Cheryl Ladd for Farrah Fawcett (Charlie’s Angels). Fawcett quit at the height of her popularity to do movies. Ladd did well as a replacement.

9. Charlie Sheen for Michael J. Fox (Spin Ciity). ABC ended the series after Sheen joined, but not before Sheen picked up an Emmy and a lot of critical praise.

10. Pernell Roberts for no one (Bonanza). Roberts was the fourth Cartwright brother, but his career went into limbo after leaving show.