Some TV shows get better when an actor or actress leaves the show. 

Here are a list of nine shows from A.V. Club:

  1. "A Different World," Lisa Bonet - The show was a spinoff of "The Cosby Show" featuring Lisa's character going off to college.  She left to have a baby, and eventually went back to "Cosby" after having the baby.
  2. "Parks and Recreation," Paul Schneider - When he left after season 2, the show brought on both Rob Lowe and Adam Scott.
  3. "The Daily Show," Craig Kilborn - Kilborn had the show from 1996-1999 and then Jon Stewart took over and it has become a daily staple.
  4. "Cheers," Shelley Long - It was Shelley's choice to leave the show which turned out to be a bad decision for her, but with the addition of Kirstie Alley and ending the Sam-and-Diane romance angle, that probably saved the show creatively.
  5. "E.R." George Clooney - Clooney was the breakout star, but his departure in 1999 didn't kill the show. Instead it survived several other original cast departures before it ended without ever really losing what made it great.
  6. "The O.C." Mischa Barton - The show actually went down in the ratings, but die-hard fans agreed that the show got better without her.
  7. "The Mary Tyler Moore Show," Valerie Harper and Cloris Leachman - They both left for their own spin-offs, which allowed more room for Betty White and Georgia Engel to break out and shine.
  8. "Star Trek: The Next Generation," Denise Crosby - Her character was more of a mixed bag, and not really a fan favorite.  When she was killed off, characters like Worf and Geordi got much more screen time.
  9. "Grey's Anatomy," Katherine Heigl - By the time Heigl left the show, her character had gotten annoying to fans, and to the public's real life perception of her as well. So no one was really sad to see her go.

To get more specific commentary on each show, and see more shows that got better after someone left, go to the A.V. Club website.