What characters from TV do you feel were indispensable; that is, what characters' absence would have (or did) basically ruin the show?

Here's some of mine:

Did:

Ritchie (Happy Days)
Mulder (The X-Files)
Fred (Sanford and Son)
Mike, Gloria, and Edith (All in the Family)
Shirley (Laverne and Shirley)
Vinnie and Gabe (Welcome Back, Kotter)
Bob Newhart (final season of The Bob Newhart Show)
Blake (Blakes 7)
Frank (Homicide: Life on the Street)


Would have:

Ann (One Day at a Time)
Alice (Alice)
Hawkeye (MASH)
Fonzie (Happy Days)
Alex (Taxi)
Barney (Barney Miller)
George (The Jeffersons)
Emily (Bob Newhart Show)
Mary (Mary Tyler Moore)
Jessica (Soap)
Andy (NYPD Blue)
Lou (Lou Grant)
Jack (Three's Company)
Mr. Humphries (Are You Being Served?)
Matt Dillon (Gunsmoke)
Ben (Bonanza)
Captain Kirk or Mr. Spock (Star Trek TOS)
Archie (All in the Family) (they almost went on without him after O'Connor had issues with Lear right before Season 5, I believe)


Now I realize it seems silly to list folks whose name is in their own show (too obvious?) but there are a few examples where the show went on without the title character, such as Welcome Back, Kotter and Blakes 7.

Did:
Barney Fife (The Andy Griffith Show)

Would Have:
Tony Nelson (I Dream of Jeannie)
Ginger Grant (Gilligan's Island)
Sam Malone (Cheers)

Did:
Barney Fife (The Andy Griffith Show)

Would Have:
Tony Nelson (I Dream of Jeannie)
Ginger Grant (Gilligan's Island)
Sam Malone (Cheers)

Great answers. Can't believe I forgot Barney.

Would have:

Barbara Cooper, One Day at a Time

Show: The character of Barbara Cooper is no longer with us
Me, grabbing remote: >click<

Ed Norton on The Honeymooners. Whether it was the sketches or the Classic 39 episodes, the scenes with Jackie Gleason and Art Carney are so funny.

Did:

Bo And Luke - The Dukes Of Hazzard

The Harts of Hart to Hart were indispensable in how they were happily married and showed it; that 1979-84 ABC series would not have been what it was had either one been absent, or had Max even been absent.

Did:

James (Good Times)

Would Have
Heathcliff Huxtable- The Cosby Show
Mork- Mork & Mindy

Did
John Boy Walton- The Waltons