MUST SEE #TBT: Remember When These Famous Faces Joined Your Favorite NBC Sitcoms?

For a solid 25 years, NBC ruled over Thursday nights and reigned over sitcoms with their "Must See TV" line ups. Between 1982 and 2006, NBC's 8pm-10pm Thursday night schedule boasts such classic sitcoms as The Cosby Show, Cheers, Seinfeld, Friends, and The Office, as well as lesser known outliers like Veronica's Closet, The Single Guy, and Boston Common.

Nobody does comedy like NBC used to, but thanks to streaming, you can catch a classic night of NBC Must See TV comedy any Thursday you want.

Enter Decider's Must See #TBT. Every Thursday, we'll focus on a specific time period (or theme) and deliver a custom Must See TV line up. Not every sitcom keeps its main cast from premiere to finale. In fact, most sitcoms lose actors and add new faces. This week we want to look back at how the introduction of new characters changed our favorite sitcoms.

Cheers

Season 4, Episode 1: "Birth, Death, Love and Rice"
Original Air Date: September 26, 1985

Woody Boyd (Woody Harrelson) is undoubtedly one of Cheers' more iconic characters, but he didn't join the cast until season four. Producers brought him on to replace the hole left by actor Nicholas Colasanto's untimely death.

Stream "Birth, Death, Love and Rice."

The Cosby Show

Season 6, Episode 1: "Denise: The Saga Continues"
Original Air Date: September 21, 1989

What do you do when your show's original cute child stars have grown up into teens and twenty-somethings? You bring a new kid into the mix. Lisa Bonet returned to The Cosby Show in 1989 and brought with her a 3-year-old step daughter played by a very young, and very electric, Raven-Symone.

Stream "Denise: The Saga Continues."

The Office

Season 3, Episode 1: "Gay Witch Hunt"
Original Air Date: September 21, 2006

Over the years, The Office saw a lot of characters join Dunder-Mifflin and then leave, and then come back for sweeps. But the first big cast shake up happened when Jim (John Krasinski) left the Scranton office to take a promotion. His new office mates? Rashida Jones, who eventually left The Office for Parks and Recreation, and Ed Helms. No one could have predicted from this episode that the annoying Andy Bernard would serve as the show's heart in later seasons, but it's still fun to look back at our first encounter with the "Nard Dog."

Stream "Gay Witch Hunt."

Parks & Recreation

Season 2, Episode 23: "The Master Plan"
Original Air Date: May 13, 2010

When Adam Scott and Rob Lowe joined the cast of Parks & Recreation at the end of season two to replace the departing Paul Schneider, no one could have predicted that they would be the final two pieces of the Parks & Rec puzzle. Lowe added a zany optimism to the show and Scott's Ben Wyatt soon morphed from an uptight curmudgeon into the most charming leading man in recent sitcom history.

Stream "The Master Plan."

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