It's hard to see beloved characters leave your favorite shows. You have created a bond with them, perhaps even projected their values onto yourself in an effort to raise the self esteem you had before, say, you fell down the Law & Order rabbit hole and started to believe the shows were actual news and not just "ripped from the headlines." But change is inevitable, and sometimes, it works out. Here are a few that worked (at least for me).

1. Current cast of Law & Order: I know, I know, who could replace Lenny Briscoe? No one, really. But the current pairing of Anthony Anderson and Jeremy Sisto as NYPD partners is the best the series has produced. They changed the feel of the show. Perhaps because we're still getting to know them, they are less predictable then previous tandems, and both evoke a certain hard-nosed quality that seems a bit more gritty and real. Plus, Anderson has chops as a stand-up comic, and could easily fill the wisecracker role, if need be.

2. David Tennant as Dr. Who: No series has ever changed leads as often as Dr. Who. It's even built into the plot, and David Tennant will be replaced at the end of 2009 by a new Time Lord, Matt Smith. But his act will be hard to follow. Tennant has a maniacal charm and comic timing perfectly suited to the character.

3. Mike Nelson takes over for Joel Hodgson on Mystery Science Theater 3000: Joel Hodgson was the creator and central voice of MST3K, and thus will always be the best space captive the Satellite of Love ever held. But Mike Nelson was a writer on the show before he ascended to the silhouettes, and several of the series' classic episodes were under his watch. Space Mutiny, with its railing deaths and poorly timed utility vehicle jousting was funny from top to bottom.

4. Jon Stewart takes over The Daily Show from Craig Kilborn: Okay, so this isn't technically a "character" replacement, but handing Stewart the reins at The Daily Show certainly changed the character of the show. Under his influence, the show relied less on rube-bashing (although that remains a favorite sport) and more on newsmakers, both in the set pieces and the interview segment. Kilborn was funny, but it's hard to imagine the show mustering the same kind of staying power if he hadn't left.

5. Charles Emerson Winchester III in for Frank Marion Burns on M*A*S*H: Burns was one of TV's best targets, a wonderful ninny and the source of endless fun for "Hawkeye" Pierce and "Trapper John" McIntyre, but Winchester was less of a caricature and every so often, was part of the fun himself.

6. "Woody" Boyd takes over for Ernie "Coach" Pantusso on Cheers: Coach was a lovable, endearing presence on Cheers, but when Nicholas Colasanto, the actor who played him, died in 1985, Woody Harrelson stepped in. Woody was clueless and endearing, long before he was menacing or couldn't jump, and was a staple of the show for eight years.

7. Deborah Fiderer for Delores Landingham on The West Wing: It took a full season to hire a permanent replacement for Mrs. Landingham, but Lily Tomlin was a perfect fit. Lily Tomlin had the gravitas to face down a cast full of strong actors in well-defined characters, and complimented Martin Sheen nicely.