| Movie | 1990 | Gremlins 2: The New Batch | Forster | |
| Movie | 1981 | Golden Gate | | |
| Movie | 1987 | Innerspace | The Cowboy | |
| Movie | 1987 | Munchies | Bob Marvalle | |
| Movie | 1994 | Revenge of the Nerds IV: Nerds In Love | Chad Penrod | |
| Movie | 1983 | Star 80 | Interviewer | |
| Movie | 1982 | Lois Gibbs and the Love Canal | Larry McGuinness | |
| Movie | 1981 | The Howling | Eddie Quist | |
| Movie | 1988 | 976-EVIL | Mark Dark | |
| Movie | 2010 | Quantum Quest: A Cassini Space Odyssey | Milton (voice) | |
| Movie | 1989 | The 'Burbs | Joe, Garbageman #2 | |
| Movie | 1985 | Legend | Meg Mucklebones | |
| Movie | 1993 | Matinee | Howard, the Theater Manager | |
| Movie | 1985 | Explorers | Starkiller / Wak / Wak and Neek's Father | |
| Movie | 2011 | Beethoven's Christmas Adventure | Smirch | |
| Movie | 1992 | Samantha | Neil Otto | |
| Movie | 1988 | Dead Heat | Lt. Herzog | |
| Movie | 2006 | A.I. Assault | Dr. John Foster | |
| Movie | 1983 | Get Crazy | O'Connell | |
| Movie | 1988 | Jack's Back | Dr. Carlos Battera | |
| Movie | 1994 | The Pagemaster | Pirate (voice) | |
| Movie | 2003 | Roddenberry on Patrol | The Doctor | |
| Movie | 2018 | Buttons | Mr. Wentworth | |
| Movie | 2022 | Discontinued | Theodore | |
| Movie | 2009 | Sensored | Wade Mixon | |
| Movie | 1989 | Loverboy | Dr. Reed Palmer | |
| Movie | 1991 | Motorama | Jerry the Policeman | |
| Movie | 2010 | Mega Shark vs. Crocosaurus | Admiral Calvin | |
| Movie | 2011 | Morlocks | Colonel Wichita | |
| Movie | 2021 | Portal Runner | TV Salesman | |
| Movie | 2008 | Ben 10: Race Against Time | Principal White | |
| Movie | 2010 | Monsterwolf | Stark | |
| Movie | 1987 | Paul Reiser: Out on a Whim | | |
| Movie | 1987 | Bates Motel | Dr. Goodman | |
| Movie | 2009 | The Awakened | Maddox | |
| Movie | 2012 | Spirit Hunters | Bob | |
| Movie | 1997 | Menno's Mind | Senator Taylor | |
| Movie | 2024 | To the Journey: Looking Back at Star Trek: Voyager | Self | |
| Movie | 2012 | Atlas Shrugged: Part II | Dr. Robert Stadler | |
| Movie | 2011 | The Candidate | Carl Tucker | |
| Movie | 1987 | The Man Who Fell to Earth | Agent Richard Morse | |
| Movie | 2012 | Rock Jocks | Guard 1 | |
| Movie | 1998 | Archibald the Rainbow Painter | Dr. Kurtz | |
| Movie | 2012 | The Legends of Nethiah | Grandpa / Sir Hanif | |
| Movie | 1986 | Back to School | Giorgio | |
| Movie | 2010 | The Captains of The Final Frontier | Self | |
| Movie | 2011 | Trail of Blood | Agent Weston | |
| Movie | 2023 | A Biltmore Christmas | Harold Balaban | |
| Movie | 2002 | Creating a Myth... the Memories of 'Legend' | Himself | |
| Movie | 1994 | Runaway Daughters | Mr. Cahn | |
| Movie | 1992 | The Witches of Eastwick | Raymond Gentry | |
| Movie | 1993 | Fatal Deception: Mrs. Lee Harvey Oswald | David Lifton | |
| Movie | 2014 | That Guy Dick Miller | Self | |
| Movie | 2014 | Age of Tomorrow | General Magowan | |
| Movie | 2022 | MEAD | Admiral Gillette | |
| Movie | 2014 | Don't Blink | Man in Black | |
| Movie | 2022 | Confess, Fletch | Count Clementi Arbogastes De Grassi | |
| Movie | 1995 | Launch of Star Trek: Voyager | Himself | |
| Movie | 1995 | E! Inside Star Trek: Voyager | Himself | |
| Movie | 1981 | The Violation of Sarah McDavid | Scott Crowell | |
| Movie | 2025 | Werewolf Game | Bill | |
| Movie | 2012 | The Inspector Chronicles | Bernard | |
| Movie | 1991 | Violation of Trust | Dr. Raymond Gilmore | |
| Movie | 2020 | Unbelievable!!!!! | Boris / Edgar Allan Putz | |
| Movie | 2010 | The Odds | Dale Kakowski | |
| Movie | 1991 | L.A. Story | Voicephone (voice) (uncredited) | |
| Movie | 2014 | Infiltrators | Reverend Quaid | |
| Movie | 2003 | Looney Tunes: Back in Action | Acme VP, Rhetorical Questions | |
| Movie | 1995 | The New Explorers: The Science of Star Trek | Self | |
| Movie | 2011 | The Captains | Self | |
| Movie | 2024 | Space Command Redemption | Yusef Sekander | |
| Movie | 2012 | Camilla Dickinson | Mr. Stephanowski | |
| Movie | 2005 | Homecoming | Kurt Rand | |
| Movie | 1996 | Star Trek: First Contact | Enterprise EMH | |
| Movie | 2016 | Hail, Caesar! | Rabbi | |
| Movie | 1994 | Wagons East! | Ben Wheeler | |
| Movie | 2015 | Occupants | Dr Alan Peterson | |
| Movie | 1988 | China Beach: Pilot | Dr. Dick Richard | |
| Movie | 2016 | The Father and the Bear | Charlie | |
| Movie | 1989 | The Cover Girl and the Cop | Denise's Date | |
| Movie | 2008 | P.J. | Stan Jamison | |
| Movie | 1992 | A Murderous Affair: The Carolyn Warmus Story | David Lewis | |
| Movie | 2016 | The Meddler | Cos | |
| Movie | 1991 | Frame Up | Frank Govers | |
| Movie | 2015 | Mansion of Blood | Samuel Corbett | |
| Movie | 1995 | Star Trek: Voyager - Inside the New Adventure | Host | |
| Movie | 2008 | Universal Signs | Father Joe | |
| Movie | 1983 | Dixie: Changing Habits | Harry Meadows | |
| Movie | 2016 | Cozmo's | Wender | |
| Movie | 1999 | Star Trek: Voyager - Dark Frontier | The Doctor | |
| Movie | 2019 | Torn | Rabbi | |
| Movie | 1997 | The Second Civil War | Godfrey | |
| Movie | 2006 | 40 Years of Star Trek | Self | |
| Movie | 1995 | Out There | Walter Danverstein (uncredited) | |
| Movie | 2019 | Ben, frankly. | Caesar | |
| Movie | 1990 | Total Recall | Johnnycab (voice) | |
| Movie | 1992 | Deadly Matrimony | Prosecutor | |
| Movie | 2017 | A Bad Feeling | Self | |
| Movie | 2020 | Superhuman: The Invisible Made Visible | Self - Special Guest | |
| Movie | 2003 | Unleashing the Beast: Making ‘The Howling’ | | |
| Movie | 1998 | Small Soldiers | Ralph, Clean Room Technician | |
| Movie | 2021 | Deck the Heart | Larry Link | |
| Movie | 2021 | After Masks | Dr. Robinson (Past Cure Segment) | |
| Movie | 1983 | The Other Woman | Chuchi | |
| Movie | 2001 | The Amati Girls | Grace's Doctor | |
| Movie | 1994 | White Mile | Tom Horton | |
| Movie | 1987 | Amazon Women on the Moon | Rick Raddnitz (segment "Roast Your Loved One") | |
| Movie | 2015 | Star Trek: Renegades | Dr. Zimmerman | |
| Movie | N/A | Bad News on the Doorstep | | |
| Movie | 2025 | How Far Does the Dark Go? | | |
| TV Show | 1976 | Alice | | 7 |
| TV Show | 2007 | Chuck | Perseus | 1 |
| TV Show | 2009 | Castle | Clark Murray | 2 |
| TV Show | 2005 | The Closer | Mr. Sheffield | 1 |
| TV Show | 2002 | The Dead Zone | Mitch McMurtry | 1 |
| TV Show | 2004 | The 4400 | Trent Appelbaum | 1 |
| TV Show | 1986 | L.A. Law | Lawyer John Dunphy | 2 |
| TV Show | 1987 | 21 Jump Street | Ralph Buckley | 1 |
| TV Show | 1991 | Home Improvement | Joe Morton | 2 |
| TV Show | 1985 | The Golden Girls | Dr. Revell | 1 |
| TV Show | 1982 | Silver Spoons | | 1 |
| TV Show | 2005 | E-Ring | | 2 |
| TV Show | 1995 | Star Trek: Voyager | The Doctor | 169 |
| TV Show | 1996 | Early Edition | Doctor | 1 |
| TV Show | 1988 | China Beach | Dick Richard | 64 |
| TV Show | 2003 | Cold Case | Arthur Lennox | 1 |
| TV Show | 1989 | Tales from the Crypt | Frank Bobo | 1 |
| TV Show | 1995 | VR.5 | | 1 |
| TV Show | 2001 | Crossing Jordan | Bruno Casnelli | 1 |
| TV Show | 2003 | Eve | Professor Dunson | 1 |
| TV Show | 2004 | CSI: NY | Sheriff Benson | 1 |
| TV Show | 1991 | Dinosaurs | Clerk (voice) | 1 |
| TV Show | 2007 | Women's Murder Club | | 1 |
| TV Show | 1983 | Scarecrow and Mrs. King | | 1 |
| TV Show | 1993 | Frasier | Charlie Koechner | 1 |
| TV Show | 2005 | Masters of Horror | | 1 |
| TV Show | 2003 | The O.C. | Bill Merriam | 1 |
| TV Show | 1982 | Newhart | | 1 |
| TV Show | 1973 | Kojak | Thomas Rindone | 2 |
| TV Show | 1997 | The Practice | Dr. Edmunds | 1 |
| TV Show | 1979 | Archie Bunker's Place | | 1 |
| TV Show | 1988 | The Wonder Years | Coach Cutlip | 13 |
| TV Show | 2001 | Smallville | Edward Teague | 2 |
| TV Show | 1997 | Ally McBeal | Barry Philbrick | 1 |
| TV Show | 1997 | Stargate SG-1 | Richard Woolsey | 7 |
| TV Show | 1998 | Seven Days | | 1 |
| TV Show | 2003 | The Lyon's Den | | 8 |
| TV Show | 1994 | ER | Abraham Zimble | 1 |
| TV Show | 2014 | The Flash | Dexter Myles | 2 |
| TV Show | 1986 | Throb | | 1 |
| TV Show | 1995 | The Outer Limits | Emmet Harley | 1 |
| TV Show | 2003 | Evil Con Carne | Cod Commando (voice) | 1 |
| TV Show | 1992 | Batman: The Animated Series | Eddie G. (voice) | 1 |
| TV Show | 2005 | Ben 10 | Leader Alien (voice) | 1 |
| TV Show | 1982 | It Takes Two | | 1 |
| TV Show | 1980 | The Dream Merchants | Mark Kessler | 3 |
| TV Show | 2001 | Justice League | Blackhawk (voice) | 1 |
| TV Show | 2001 | Justice League | Blackhawk / Nazi Soldier (voice) | 1 |
| TV Show | 2001 | Justice League | Amazo (voice) | 2 |
| TV Show | 2004 | Justice League Unlimited | Amazo (voice) | 2 |
| TV Show | 2008 | The Mentalist | Jason Cooper | 4 |
| TV Show | 2012 | Perception | A. Z. Weyland | 1 |
| TV Show | 1985 | Amazing Stories | Tony Sepulveda | 1 |
| TV Show | 2022 | The Shuttlepod Show | Self | 1 |
| TV Show | 2014 | The Flash | Dexter Myles (voice) | 1 |
| TV Show | 1978 | Taxi | Philip Polevoy | 1 |
| TV Show | 2003 | NCIS | Dale Harding | 1 |
| TV Show | 2011 | Body of Proof | Henry Pedroni | 1 |
| TV Show | 1996 | Sabrina, the Teenage Witch | Bob Jacobs | 2 |
| TV Show | 1995 | The Savage Dragon | (voice) | 13 |
| TV Show | 2009 | Stargate Universe | Richard Woolsey | 1 |
| TV Show | 2004 | Stargate Atlantis | Richard Woolsey | 26 |
| TV Show | 1991 | Dinosaurs | Ted (voice) | 1 |
| TV Show | 1991 | Dinosaurs | Muse (voice) | 1 |
| TV Show | 2017 | The Good Fight | Arbiter Alan Mannheim | 1 |
| TV Show | 2012 | The Client List | Judge Hughes | 1 |
| TV Show | 2021 | The Center Seat: 55 Years of Star Trek | Self | 2 |
| TV Show | 2020 | Star Trek Day | Self | 1 |
| TV Show | 1995 | What a Cartoon! | Pfish (voice) | 2 |
| TV Show | 2005 | Supernatural | Wayne Whittaker Jr. | 1 |
| TV Show | 2010 | Justified | Karl Hanselman | 1 |
| TV Show | 2000 | Buzz Lightyear of Star Command | Professor Reddschift (voice) | 1 |
| TV Show | 2017 | The Orville | Ildis Kitan | 2 |
| TV Show | 2007 | Pushing Daisies | Detective Puget | 1 |
| TV Show | 2017 | Young Sheldon | Professor Salzman | 1 |
| TV Show | 2018 | Station 19 | Mr. Nelligan | 1 |
| TV Show | 1993 | The Adventures of Brisco County, Jr. | Puel | 1 |
| TV Show | 1993 | Star Trek: Deep Space Nine | Dr. Lewis Zimmerman / EMH Mark I | 1 |
| TV Show | 2011 | Jessie | Cyril Lipton | 1 |
| TV Show | 1987 | Mr. President | Reinbeck | 1 |
| TV Show | 2020 | Stars in the House | Self | 1 |
| TV Show | 2005 | Grey's Anatomy | Mr. Nelligan | 2 |
| TV Show | 2021 | CSI: Vegas | Carlo Rey | 1 |
| TV Show | 2011 | Femme Fatales | Hieronymus Hawks | 1 |
| TV Show | 2020 | Mythic Quest | Principal Taggart | 1 |
| TV Show | 2013 | The Captains Close Up | Self | 1 |
| TV Show | 2005 | Bones | Dr. Lawrence Rozran | 1 |
| TV Show | 1999 | The West Wing | E. Bradford Shelton | 1 |
| TV Show | 2022 | Quantum Leap | Dr. Edwin Woolsey | 1 |
| TV Show | 2011 | Happy Endings | Mr. Logan | 1 |
| TV Show | 2016 | Lucifer | Yuri | 1 |
| TV Show | 2021 | Star Trek: Prodigy | The Doctor (voice) | 17 |
| TV Show | N/A | Star Trek: Starfleet Academy | The Doctor | 1 |
| TV Show | 2011 | Austin & Ally | Dr. Grant | 1 |
| TV Show | 2019 | Dickinson | Ithamar Conkey | 10 |
| TV Show | 2016 | Justice League Action | Harvey Dent / Two-Face (voice) | 1 |
| TV Show | 2010 | Hawaii Five-0 | C.I.A. Man | 1 |
| TV Show | 2011 | Harry's Law | Annie's Psychiatrist | 1 |
