Harlin Polk, played by Gary Grubbs. A major client of Will's in season one, who ultimately fires him.

Mrs. Freeman, played by Jo Marie Payton. An executive assistant at Doucette & Stein, her most commonly uttered phrase is "Mm-hmm."

Zandra Zoggin, played by Eileen Brennan. Jack's crusty acting coach, a former Hollywood star. After Jack takes over her class, Zandra loses her interest in life and ends up in an actor's retirement village.

Dr. Jay Markus, played by Tom Skerritt. Leo's father, and Grace's eventual father-in-law, whom she meets during brunch, thinking he is one of Leo's "old friends."

Eleanor Markus, played by Judith Ivey. Leo's mother and a noted author of three books on theatre, she meets Grace during brunch alongside her husband. She also is the first to tell her new daughter-in-law her son's actual name, Marvin.

Mr. Stein, played by Gene Wilder. The senior partner at Will's firm, an eccentric man who takes a liking to Will. He refers to Will as "Gay Will," but without at first realising that Will is actually gay. He and Karen fancied each other, but nothing came of it. He was away from the office for some time prior to season 5 due to a mental breakdown.

Margot, played by Lily Tomlin. A senior partner at Will's firm who apparently takes over after Mr. Stein. She promotes Will to partner.

Dorleen, played by Parker Posey. Jack's bitchy, chain-smoking boss during his brief tenure at Barneys New York.

Lorraine Finster, played by Minnie Driver. Stan's mistress, a slutty prison cafeteria worker (and, it is implied, prostitute) who instantly forms a hatred of Karen. Was Karen's stepdaughter very briefly (for about 20 minutes) when her father, Lyle, married Karen, although Lorraine was unable to attend the wedding due to an aggressive strain of herpes that kept her from flying. According to the episode "The Accidental Tsuris," she was raised as a girl despite being genetically male or perhaps hermaphroditic.

Mr. Zamir, played by Marshall Manesh. An obnoxious tenant in Will and Grace's building with a tendency to take off his shirt and to steal Will and Grace's newspapers.

Benji, played by Brian A. Setzer. Beverley Leslie's "business associate" and boytoy.

Joanne, played by Emily Rutherfurd. A student of Zandra's acting class, who becomes a devoted follower of Jack and his "McFarland method."

Julius, played by Neil Vipond. Bobbi Adler's close friend and pianist.

Gary, played by Jamie Kaler. Will's coworker at Doucette and Stein.

Nurse Sheila, played by Laura Kightlinger. A rather creepy nurse who works at the sperm bank (where Will visits, intending to donate sperm to his high-school friend Claire), who openly admits she is a whore in season 4 (when Will and Grace are planning to have a baby together), and thereafter seems to appear whenever Will goes into a hospital. She was pregnant in season 8 and attended birth classes alongside Grace. Her brother, a doctor played by guest-star Jack Black (and real-life former girlfriend) claims he would be "tappin' that big time" if they weren't related.

Jennifer Lopez, as herself. An old friend of Rosario's from their days in the Bronx, Lopez agreed to sing at Karen's wedding to Lyle, and then took Jack under her wing as a backup dancer. Months later, however, after learning of her dog's death, Lopez received a badly timed song submission from Karen and Jack, leading her to fire the latter from her team.

Janet Jackson, as herself. Jennifer Lopez refers Jack to Jackson after he is fired from J-Lo's dance crew. Jackson demands Jack and another student (whom Karen used to date, played by Will Arnett) have a dance-off to decide who gets to stay.

Dave, played by Matthew Botuchis. The only straight worker at OutTV, the gay network where Jack works in the last seasons. Jack, unimpressed with his heterosexuality, refers to Dave as "Elizabeth."

Jamie, played by John Ducey. The station manager at OutTV.

Tim, played by Mark Harelik. A senior assistant at OutTV.

Jimmy, played by Sam Pancake. A senior assistant at OutTV.

Smitty, played by Charles C. Stevenson Jr. A bartender who regularly serves Karen at different establishments. She has been known to call other bartenders "Smitty," even when they tell her it isn't their name. If Karen is depressed, Smitty will tell her a tragic story about his own life, which she will laugh at, thinking it is a joke.

Klause von Puppy: A dog. His first appearance was in The Truth About Will & Dogs where he was only a puppy owned by Will. At the end of that episode, he gave the dog to Jack. In a few other episodes, he refers to him as Klause von Puppy.

Owen, played by Matt Damon, in A Chorus Lie (Season Four). He plays a straight man, posing as a gay man to get into the Gay Men's Chorus. Jack uses Grace to "in" Owen and exposes him during a solo audition, but Owen is allowed to remain in the chorus anyway due to the "tolerance" policy.