I was watching Seinfeld today and noticed a ton of 'stars' have been on the show as guests. Kirsten Davis and Chris Parnell were on the episode I just watched. I know Debra Messing, Jane Ives were on a episode as well as a ton of others. I'm not saying Seinfeld is responsible for making these people stars, just kind of odd how many people went on to decent careers. So what sitcom has had the most people move on to bigger careers?

M*A*S*H had quite a few. Probably more than Seinfield as it ran for 11 seasons.

The few I can think of off the top of my head:
John Ritter
Patrick Swayze
James Cromwell
Rita Wilson
Teri Garr
Pat Morita

Taxi
Happy Days

cheers

This question needs more parameters. "Friends", for instance, guested more big names than most of the shows named.

Ned and Stacy?

Mary Tyler more was pretty great:

Almost every character re-appeared on another sucessful follow up TV show:
Ed Asner - Lou Grant
Murray/Gavin - Love Boat
Ted - Too Close
Rhoda - Rhoda
Betty White - Golden Girls

I believe 'Battle of the Network Stars' had the most stars come from it ...

Since when is Kristen Davis a 'Star' ?

Considering it ran for 15 years and spawned 6 spin-offs (7 if you count "704 Houser"), ALL IN THE FAMILY has to be up there.

Simpsons?

Yep. That was the first one I thought of. Stellar cast. Plus you had John Amos who went on to a hit show in Good Times.

I think we're talking about people who had cameo roles while they weren't that famous, and went on to bigger things. IIRC, most of the Friends cameos are famous actors who wanted to make a guest appearance. For those kinds of appearances, Will and Grace must be up there... I didn't really watch the show, but it seemed like they had a new celebrity on every week.

I'd say Law & Order, but it's not a sitcom (or is it?).

Miami Vice. I know it wasn't what the OP was asking for but it had a lot of stars that were unknown at the time it was on.

Ving Rhames, Julia Roberts, Helena Bonham Carter, Esai Morales, John Leguizamo are a few I remember that have decent careers today that appeared on that series.

Another guest star who went on to have a decent career was a guy named Bruce Willis.

Damn, I forgot the most obvious one besides J. Roberts.

There are a ton of them in Seinfeld. It seems like most episodes have someone who went on to bigger and better roles. I wouldn't say that Seinfeld "produced" them as they are usually bit parts, but, like L&O, there are a ton of actors on TV today who were once in a Seinfeld episode.

jimmy smits was the partner in the pilot.

weren,t they the main characters and not guests though?

Since non-sitcoms are being mentioned, I'll throw The Rockford Files into the mix. There were a number of future stars that appeared on that great show, including two of my favorites, James Woods & Ed Harris.

Let's not forget Liam Neeson, who also did a guest scint on Miami Vice.

Growing Pains had Brad Pitt, Leo, and Matthew Perry.

They also had a guy named Boner on the show. And Ben glued his butt to the coffee table in one episode. Pretty edgy.

Let us not forget that Boner AKA Andrew Koeing once played the Joker!