Seinfeld: Phil Morris, Teri Hatcher, Armin Shimerman (Star Trek), Bryan Cranston (Malcolm in the Middle), Paula Marshall, Bob Balaban, Patrick Warburton, Marrisa Thomei, Jerry Stiller, Kristin Davis (Sex and the City), A.J. Langer, John Voight, Debra Messing, Lloyd Bridges, Janeane Girafolo
Highlights: Seinfeld has a longer list of guest stars that I could possibly make room to mention here or would even know of without far more extensive research, but it is interesting to note that many comic actors like Phil Morris, Jerry Stiller, Patrick Warburton, and John O'Hurley are most recognizeable through their Seinfeld guest roles. Seinfeld was also lucky to have some of the most attractive ladies in Hollywood (i.e. Paula Marshall, Teri Hatcher, Kristin Davis) playing opposite him. John Voight appeared as himself in one episode and bit Kramer's hand.
Newsradio: Bob Costas, David Cross, Patrick Warburton, James Caan, Brian Poehnson (Sara Silverman Show, Just Shoot Me), John Stewart, Lauren Graham, Jerry Seinfeld, Tiffiany Amber-Thiessen (Saved by the Bell), Kevin McDonald (Kids in the Hall), Scott Adams (creator of Dilbert), Janeane Girafolo, Bryan Callan (Mad TV)
Highlights: Without a doubt, Patrick Warburton and Lauren Graham made the most of their recurring roles. Warburton, in what I think is a very typecast role, plays an extremely affable and friendly evildoer (it all makes sense in Newsradio's bizarro world) and later plays a homeless bum and Lauren Graham plays a prissy efficiency expert who is more concerned with her "best friend" status with Lisa that she conjured than anything else. Before John Stewart was an intellectual icon to college students nationwide, he was Andy Dick's brother on Newsradio in a mismatch of the ages. Lastly, let's not forget that media outlets claiming 30 Rock was Seinfeld's first guest appearance on a sitcom were incorrect. He also played himself on an episode of Newsradio.
My Name is Earl: Giovanni Ribisi, Christain Slater, Norm McDonald, Amy Sedaris (Strangers with Candy), Katherine Kinney (Drew Carey Show), Mike O’Malley (Yes, Dear), John Leguazimo, Ben Foster (X-Men: The Last Stand)
Highlights: Not a lot of stunt casting has taken place on My Name is Earl, because the show doesn't neccessarily need it. Christian Slater is the most high-profile star to appear if this list is as complete as I think it is. Norm McDonald, who can out deadpan anyone on the planet, was incredibly well-used as a bar owner who transforms through the episode from cruel to benevolent and back again without much change in facial expression.
The Office: David Koechner, Conan O’Brien, Amy Adams (Junebug, Talladega Nights), Rob Riggle (SNL, Daily Show), Tim Meadows, Nancy Walls (SNL), Chip Esten (Whose Line is it Anyways)
Highlights: The Office is pretty vehement about avoiding stunt casting because it would take away the reality of the show. When Conan O'Brien appeared as himself in a very brief non-speaking cameo, the only self appearance on the list above, it was because Michael Scott was in New York and the documentarian caught Conan in his lens. However, aside from up-and-comer Amy Adams, and SNL alumni David Koechner and Nancy Walls (Carrell's real-life wife) in recurring roles, guys like Rob Riggle as a fun cruise captain and Tim Meadows as a respective client have added a little bit of star power in one-episode roles.
3rd Rock from the Sun: Wayne Knight, John Cleese, Cindy Crawford, Kurtwood Smith (That 70’s Show), Jan Hooks (SNL), William Shatner, Laurie Metcalf (Roseanne), Phil Hartman, Dennis Rodman, Mike Ditka, Kevin Nealon, Bryan Cranston
Highlights: Cindy Crawford probably tested her acting chops more than ever before as Harry's romantic interest and Wayne Knight enjoyed life comfortable after Seinfeld in this heavily recurring role as Sally's long-time boyfriend.