Take a look back at some of the more memorable casting changes in the history of television.
In 2011, Steve Carell stepped away from his "The Office" role as Michael Scott, a part he had played since 2005, to do movies full time.
James Spader replaced Carell, playing the intense Robert California. However, California did not fill the Michael Scott's position of regional manager of Dunder Mifflin -- that position went to Ed Helms' Andy Bernard. Instead, Spader's character became the CEO of the paper company, but lasted only one season.
Charlie Sheen was fired and his character killed off from "Two and Half Men" after a storm of controversy in 2011. His replacement for the show's ninth season?
Ashton Kutcher, no stranger to TV sitcoms thanks to his run on "That '70s Show," stepped into the hole left by Sheen's firing, playing Internet billionaire Walden Schmidt.
Sheen was on the other end of a casting change with the political comedy "Spin City" back in 2000. Who did he replace that time?
Sheen took over for Michael J. Fox, who left the hit show due to his progressing Parkinson's disease.
"Bewitched" fans will remember that the show featured two different "Darrins" during its eight-year run. Dick York played the character first, between 1964 and 1969.
Dick Sargent took over the role from 1969 through 1972, after York was forced to leave because of a severe back condition.
The soundstage for "Charlie's Angels" might as well had a revolving door with all the show's changes, starting with Farrah Fawcett leaving after the show's first season ended in 1977.
Although Fawcett would eventually return for three-episode stints in the show's third and fourth seasons, she was more or less replaced by Cheryl Ladd (center), who played her character's kid sister.
When Kate Jackson left after season three, leaving only Jaclyn Smith from the original cast, her job was handed to Shelley Hack (left), better known as Revlon's "Charlie girl."
Hack lasted only one season, with Tanya Roberts (left) coming on board for the fifth and final season of the show in 1980-81.
"Cheers" saw a couple major casting changes during its 11-year run, including one due to the 1985 death of Nicholas Colasanto, who played dim-witted bartender Ernie "Coach" Pantusso.
Rather than recasting the role, the producers hired then-unknown Woody Harrelson to play the role of equally dim-witted Indiana farm boy Woody Boyd starting with season four.
The bigger casting change came when Shelley Long, who played over-educated waitress Diane Chambers, left in 1987 following season five to focus on movies.
She was replaced with Kirstie Alley, who played businesswoman and on-again-off-again bar manager Rebecca Howe over the show's final six seasons.
"M*A*S*H" saw its first of several changes when Wayne Rogers, who played "Trapper" John McIntyre, left after season three, fed up over being a sidekick to Alan Alda's "Hawkeye" Pierce.
In came Capt. B.J. Hunnicutt, played by Mike Farrell, as Hawkeye's new straight man and comedic partner.
Chafing over his own supporting role, McLean Stevenson plotted his exit during season three, causing his Lt. Col. Henry Blake to die offscreen when his plane home was shot down over the Sea of Japan.
Replacing him eventually as new commanding officer for the 4077th was Col. Sherman T. Potter, played by Harry Morgan from season four through the end of the series.
Feeling he had taken the character of Frank Burns as far as he could, Larry Linville declined to return after his contract was up following season five in 1977.
In Burns' absence, Maj. Charles Emerson Winchester III, played by David Ogden Stiers (right), became the new foil for Hawkeye and B.J. during the show's final six seasons.
After having a falling out with the show's producers, Michael Moriarty, who played executive assistant D.A. Ben Stone on "Law & Order," left the show at the end of the 1993-94 season.
Sam Waterston stepped in to play the new executive assistant D.A. Jack McCoy and would stick with the show through the rest of its 16 seasons.
David Caruso helped make "NYPD Blue" a hit in its first season in 1993. But his reported tantrums and diva-like behavior behind the scenes didn't win him any friends on set before bolting for a movie career that never panned out.
Jimmy Smits stepped in to play Det. Bobby Simone and hung around for five seasons. It would hardly be the last casting change for the show, which saw Mark-Paul Gosselaar and Ricky Schroeder step in for stints opposite series mainstay Dennis Franz.
A contract dispute in the spring of 1982 saw John Schneider and Tom Wopat, who played Bo and Luke Duke, walk before season five of "The Dukes of Hazzard" began filming.
The producers replaced them for most of the fifth season with lookalike cousins Coy and Vance Duke, played by Byron Cherry and Christopher Mayer, before Wopat and Schneider returned.
John Ritter and Joyce DeWitt stuck around for all eight seasons of "Three's Company," but Suzanne Somers was fired after the fifth season following a prolonged contract dispute.
Somers' character, Chrissy Snow, was replaced by her clumsy cousin Cindy Snow, played by Jenilee Harrison (center).
As Harrison's character was gradually phased out during season six, in came nurse Terri Alden, played by Priscilla Barnes, who would stay for the show's final three seasons.
An earlier cast change for the show came in 1979 when apartment landlords Stanley and Helen Roper (Norman Fell and Audra Lindley) got their own spin-off show following season three.
To fill the hole, Don Knotts was added as goofy new landlord Ralph Furley, who seemed to have a knack for walking in on Jack Tripper in compromising situations.
The WB witch drama "Charmed" debuted in 1998 with a cast of Holly Marie Combs, Shannen Doherty and Alyssa Milano.
Doherty left following the third season for undisclosed reasons and Rose McGowan joined the show for its final five seasons.
For the first three seasons of the Will Smith sitcom "The Fresh Prince of Bel-Air," the role of Vivian Banks, the aunt of Smith's character, was played by Janet Hubert-Whitten (upper left).
When Hubert-Whitten left in 1993 to spend more time with her family, and also reportedly due to creative differences with Smith, Daphne Maxwell Reid (third from left) took over the role.
During the first four seasons of "Married ... With Children," Steve and Marcy Rhoades were the Bundys' yuppie neighbors.
However, when David Garrison asked out of his contract to focus on theatrical roles, he was eventually replaced with Jefferson D'Arcy, a pretty-boy scam artist played by Ted McGinley.
Lecy Goranson (upper left) originally played Becky Connors on "Roseanne" but left before the show's fifth season in 1992 to attend Vassar College.
Although Goranson would return to the role off and on, the show also turned to Sarah Chalke (now known more for the sitcom "Scrubs") to fill the role of Becky over the show's last few seasons.
Valerie Harper starred in the sitcom "Valerie" when it debuted in 1986. Harper played a mother juggling her career and family, including Jason Bateman as one of her sons.
But due to a dispute with producers, Harper's character was killed off in a car crash after the second season, clearing the way for Sandy Duncan and an eventual name change to "The Hogan Family."
William Petersen portrayed Dr. Gil Grissom on "CSI" from the time it launched in 2000 through the show's ninth season, when he left to focus on stage acting.
Although Petersen has returned to the show in guest spots, the lead character in the show became Laurence Fishburne's Dr. Ray Langston ... for three seasons at least.
Fishburne, in turn, was replaced by Ted Danson, who joined the show for its 12th season in 2011 as D.B. Russell, the new night shift supervisor.
His character's abduction by aliens in the seventh season of "The X-Files" allowed David Duchovny to become a recurring character for the show's final two seasons.
After Duchovny's semi-departure, the show introduced two new central characters, FBI agents John Doggett (Robert Patrick) and Monica Reyes (Annabeth Gish), to join Gillian Anderson's Dana Scully.
"CHiPs" was marked with several casting changes over its six seasons, including Erik Estrada's seven-episode strike in 1981-82 and the departure of Larry Wilcox during the show's final season.
"Cheers" wasn't the only show to lose a character after an actor's death. After Freddie Prinze committed suicide in 1977, he was replaced on "Chico and the Man" by child actor Gabriel Melgar as a different character nicknamed Chico.
And on "NewsRadio," Phil Hartman's death between seasons four and five had his character suffer a sudden heart attack offscreen. He was replaced with a new character played by Hartman's close friend, Jon Lovitz.
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