Filmography118 titles
| Year | Title | Character | Age at release |
|---|---|---|---|
| 2026 | The Sixty Year Mission: How Star Trek Changed Television and the WorldMovie | Self | 78 |
| 2024 | X-Men '97Series | Rama-Tut (voice) | 76 |
| 2022 | The Shuttlepod ShowSeries | Self | 74 |
| 2022 | Star Trek: Strange New WorldsSeries | Q (voice) | 74 |
| 2020 | Star Trek: PicardSeries | Q | 72 |
| 2020 | Ayreon: Electric Castle Live And Other TalesMovie | Narrator | 72 |
| 2019 | The Ready RoomSeries | Self | 71 |
| 2018 | ButtonsMovie | Dr. Johnson | 70 |
| 2018 | My Little Pony: Best Gift EverMovie | Discord (voice) | 70 |
| 2017 | Olaf's Frozen AdventureMovie | Mr. Olsen (voice) | 69 |
| 2016 | Justice League ActionSeries | Brainiac (voice) | 68 |
| 2016 | 50 Years of Star TrekMovie | Self | 68 |
| 2014 | Star Trek: The Next Generation - All Good Things...Movie | Q | 66 |
| 2013 | The Captains Close UpSeries | Self | 65 |
| 2012 | Zombie HamletMovie | Jerry | 64 |
| 2012 | CLONED: The Recreator ChroniclesMovie | Dr. Frank Miller | 64 |
| 2012 | Bronies: The Extremely Unexpected Adult Fans of My Little PonyMovie | Himself | 64 |
| 2011 | Underground Entertainment: The MovieMovie | John | 63 |
| 2011 | Franklin & BashSeries | Gallen | 63 |
| 2011 | The CaptainsMovie | Self | 63 |
| 2011 | The Secret CircleSeries | Royce Armstrong | 63 |
| 2010 | My Little Pony: Friendship Is MagicSeries | Discord (voice) | 62 |
| 2010 | Young JusticeSeries | Mr. Twister / Brom Stikk (voice) | 62 |
| 2010 | Law & Order: LASeries | Avery Staynor | 62 |
| 2009 | Crank: High VoltageMovie | Fish Halman | 61 |
| 2009 | GamerMovie | Chief Of Staff | 61 |
| 2008 | The MentalistSeries | Edward Feinberg | 60 |
| 2008 | Breaking BadSeries | Donald Margolis | 60 |
| 2008 | In Plain SightSeries | Ran Bachman | 60 |
| 2008 | PathologyMovie | Dr. Quentin Morris | 60 |
| 2007 | GreekSeries | Himself | 59 |
| 2006 | The UnitSeries | Elliott Gillum | 58 |
| 2006 | TorchwoodSeries | Allen Shapiro | 58 |
| 2006 | SharkSeries | Warren Kovak | 58 |
| 2005 | The CloserSeries | Dr. Dawson | 57 |
| 2004 | The EavesdropperMovie | Dr. Gene Kramer | 56 |
| 2003 | Duck DodgersSeries | Sinestro (voice) | 55 |
| 2003 | Burl'sMovie | Mr Cooper | 55 |
| 2002 | Without a TraceSeries | Brian Gaghan | 54 |
| 2001 | Special Unit 2Series | King of the Links | 53 |
| 2001 | The DivisionSeries | Tom Burke Sr. | 53 |
| 2001 | The GuardianSeries | Frank Newburg | 53 |
| 2001 | Crossing JordanSeries | Thaxton | 53 |
| 2001 | Good AdviceMovie | Ted | 53 |
| 2000 | CSI: Crime Scene InvestigationSeries | Robert Lansdale | 52 |
| 2000 | AndromedaSeries | Uncle Sid Barry / Sam Profitt | 52 |
| 2000 | Secret Agent ManSeries | Marshall Gilder | 52 |
| 2000 | Woman on TopMovie | Alex Reeves | 52 |
| 1999 | Family GuySeries | Pewterschmidt Industries Executive (voice) | 51 |
| 1999 | The West WingSeries | Al Kiefer | 51 |
| 1999 | Judging AmySeries | Dr. Eagan | 51 |
| 1999 | The Big Guy and Rusty the Boy RobotSeries | — | 51 |
| 1999 | Final RunMovie | George Bouchard | 51 |
| 1998 | Saving Private RyanMovie | Letter-reader (voice) (uncredited) | 50 |
| 1998 | CharmedSeries | Odin | 50 |
| 1998 | Sports NightSeries | Bert Stors | 50 |
| 1998 | Gen¹³Movie | Colonel John 'Jack' Lynch (voice) | 50 |
| 1998 | You Lucky DogMovie | Lyle Windsor | 50 |
| 1998 | The Lost WorldMovie | Lord John Roxton | 50 |
| 1997 | Ally McBealSeries | Jackson Poile | 49 |
| 1997 | The PracticeSeries | Dr. Walsh | 49 |
| 1997 | Stargate SG-1Series | Frank Simmons | 49 |
| 1997 | The Angry BeaversSeries | — | 49 |
| 1997 | WorkingSeries | Kevin | 49 |
| 1997 | Fired UpSeries | Mr. Lux | 49 |
| 1997 | TrekkiesMovie | Self | 49 |
| 1997 | Final DescentMovie | Capt. George W. Bouchard | 49 |
| 1996 | The Real Adventures of Jonny QuestSeries | Dr. Benton Quest (voice) | 48 |
| 1996 | Raven HawkMovie | Stansfield | 48 |
| 1996 | Star Trek: 30 Years and BeyondMovie | Self | 48 |
| 1995 | The Outer LimitsSeries | Donald Finley | 47 |
| 1995 | Star Trek: VoyagerSeries | Q | 47 |
| 1995 | Murder OneSeries | Mitchell Garron, Esq. | 47 |
| 1995 | LegendSeries | Janos Bartok | 47 |
| 1995 | Never Say Never: The Deidre Hall StoryMovie | John de Lancie (uncredited) | 47 |
| 1994 | DuckmanSeries | Tyler Fitzgerald (voice) | 46 |
| 1994 | Touched by an AngelSeries | Justinian Jones | 46 |
| 1994 | Without WarningMovie | Barry Steinbrenner | 46 |
| 1994 | Deep RedMovie | Thomas Newmeyer | 46 |
| 1994 | SchemesMovie | Arthur Martin | 46 |
| 1993 | Dave's WorldSeries | Mr. McFadden | 45 |
| 1993 | Star Trek: Deep Space NineSeries | Q | 45 |
| 1993 | ArcadeMovie | Difford | 45 |
| 1993 | FearlessMovie | Jeff Gordon | 45 |
| 1992 | Batman: The Animated SeriesSeries | Eagleton (voice) | 44 |
| 1992 | Missing PiecesMovie | Paul / Walter Thackary | 44 |
| 1992 | The Hand That Rocks the CradleMovie | Dr. Victor Mott | 44 |
| 1991 | The Fisher KingMovie | TV Executive | 43 |
| 1990 | Taking Care of BusinessMovie | Ted Bradford Jr. | 42 |
| 1990 | Angel of DeathMovie | Jeffrey | 42 |
| 1989 | Get Smart, Again!Movie | Maj. Waterhouse | 41 |
| 1989 | Blood RedMovie | (uncredited) | 41 |
| 1989 | Christine CromwellSeries | — | 41 |
| 1989 | The Nutt HouseSeries | Norman Shrike | 41 |
| 1988 | Mission: ImpossibleSeries | Drake | 40 |
| 1987 | Star Trek: The Next GenerationSeries | Q | 39 |
| 1986 | MatlockSeries | Dr. Albert Levinson | 38 |
| 1986 | L.A. LawSeries | Mark Chelios | 38 |
| 1986 | Houston: The Legend of TexasMovie | John Van Fossen | 38 |
| 1985 | MacGyverSeries | Brian Ashford | 37 |
| 1985 | The Twilight ZoneSeries | (segment "Dead Run") | 37 |
| 1984 | Murder, She WroteSeries | Binky Holborn | 36 |
| 1983 | The Thorn BirdsSeries | Alastair MacQueen | 35 |
| 1981 | Nero WolfeSeries | Tom Irwin | 33 |
| 1981 | The Miracle of Kathy MillerMovie | Dr. Christensen | 33 |
| 1980 | NightsideMovie | Willy Potts | 32 |
| 1979 | The Lazarus SyndromeMovie | EKG Doctor (uncredited) | 31 |
| 1979 | The Onion FieldMovie | LAPD Lieutenant | 31 |
| 1978 | Little WomenSeries | Frank Vaughn | 30 |
| 1978 | The BastardSeries | Lt. Stark | 30 |
| 1978 | Battlestar GalacticaSeries | Officer | 30 |
| 1978 | SST: Death FlightMovie | Bob Connors | 30 |
| 1977 | AspenSeries | Ray Chilton | 29 |
| 1977 | The Man with the PowerMovie | Clark | 29 |
| 1974 | The Six Million Dollar ManSeries | Diver | 26 |
| 1973 | Police StorySeries | Sgt. Ralski | 25 |
| 1972 | Emergency!Series | Dr. DeRoy | 24 |
| 1972 | Le Grand ÉchiquierSeries | Self | 24 |