The Office has featured a number of talented actors know for other projects. Below is a list of actors that have had a sinlge appearance or only a few appearances throughout the series. Season 1 saw Amy Adams' first appearance as Katy in, "Hot Girl".
- In Office Olympics Nancy Walls guest stars as Carol Stills, Michael's real estate agent.
- In The Fire and Booze Cruise Amy Adams guest stars as Katy.
- In Booze Cruise Rob Riggle guest stars as Captain Jack.
- In The Client Tim Meadows guest stars as Christian.
- In E-Mail Surveillance Ken Jeong guest stars as Bill from Michael's improv class
- In The Convention Jerome "The Bus" Bettis guest stars as himself.
- In Business Trip Wendi McLendon-Covey guest stars as Marie the Concierge
- In Stress Relief, Cloris Leachman, Jack Black, and Jessica Alba appear in the fictional movie "Mrs. Albert Hannaday"
- In New Boss and Two Weeks Idris Alba stars as Charles Miner
- In Sabre Christian Slater guest stars as himself.
- The Office "Mafia" Mike Starr guest stars as Insurance Salesman ( Mr Grotti )
- The Delivery pt 2 Mellisa Rauch ( New mom sharing the room with Pam )
- In Nepotism Evan Peters guest stars as Michael's nephew Luke Cooper.
- In The Sting Timothy Olyphant guest stars as Danny Cordray.
- In The Seminar Ricky Gervais guest stars as David Brent.
- In Training Day Will Ferrell guest stars as Deangelo Vickers, the new regional manager.
- In Search Committee several of the interviewees are guest stars, they include Will Arnett as Henry, Ray Romano as Merv Bronte, Jim Carrey as The Finger Lakes Guy, and Ricky Gervais as David Brent.
- In Mrs. California Maura Tierney guest stars as Susan California.
- In Garden Party Josh Groban guest stars as Andy's brother Walter Bernard Jr. and Stephen Collins guest stars as Andy's father Walter Bernard Sr.
- In Turf War Chris Bauer guest stars as Harry Jannerone.
- In Here Comes Treble (Episode) Stephen Colbert guest stars as Broccoli Rob, Andy's friend and a past member of the accapella group Here Comes Treble.
- In The Boat Josh Groban reprises his role as Andy's brother.
- In Lice Julius Winfield Erving aka Dr. J. of the NBA guest stars as himself.
- In Promos MLB player Ryan Howard guest stars as himself.
- In Livin' the Dream Michael Imperioli guest stars as Sensei Billy
- In Finale Joan Cusack guest stars as Erin's mother, Ed Begley Jr. guest stars as Erin's father, Angela Kinsey guest stars as Angela's sister Rachel, and Nancy Walls reprises her role as Carol Stills.