Max Pross is Office Worker in The Barber (Season 5 Episode 8).
Megan Cole is Peggy in The Susie (Season 8 - Episode 15) and in The Apology (Season 9 - Episode 9).
Megan Mulally is Betsy, the hard of hearing George's girlfriend in The Implant (Season 4 Episode 19).
Melanie Smith is Rachel Goldstein in 3 episodes. The first: The Raincoats (Season 5 Episodes 18-19).
Michael Chiklis is a Steve Pocatello in The Stranded (Season 3 Episode 10).
Michael Costanza is Truck Driver in The Parking Space (Season 3 - Episode 21).
Michael D. Roberts is Roger Ipswich, Peterman's accountant in The Chicken Roaster (Season 8 - Episode 8).
Michael Des Barres is restaurateur in The Smelly Car (Season 4 Episode 21).
Michael Fairman is Mr. Penske (the owner of Penske file) in The Barber (Season 5 - Episode 8).
Michael James McDonald is Jesse in The Wig Master (Season 7 - Episode 18) and Player in The Understudy (Season 6 - Episode 23).
Michael McShane is Franklin Delano Romanowski in The Betrayal (Season 9 Episode 8).
Michael Milhoan is the security guard in The Stranded (Season 3 Episode 10).
Michael Mitz is Phone Guy in The Chinese Restaurant (Season 2 Episode 11) and Photographer in The Puffy Shirt (Season 5 Episode 2).