(written from a Production point of view)
Harper's film debut was the 1976 drama The Time of Your Life (with Norman Snow and Nicolas Surovy). However, nearly ten years followed before Harper again worked on a film, and that was 1984's Firstborn (with Teri Garr and Peter Weller). Half that number of years passed between Harper's next film, which was Last Exit to Brooklyn (1989, with Jerry Rector, Camille Saviola, and Mike Starr). Next for Harper that same year was his first telefilm Manhunt: Search for the Night Stalker (with Jake Dengel and Angela Paton). The final film for Harper that year was the big screen biopic Blaze (with Jerry Hardin).
In the 1990s, Harper gained his first comedic role in the gender-bending Switch (1991, with Lily Mariye, Faith Minton, and Robert Towers). That year also, Harper was seen in the thriller Servants of Twilight (with Bruce Greenwood, Patrick Massett, and Carel Struycken). Harper's next movies were telefilms that year, starting with the biopic The Ernest Green Story (with Avery Brooks and Tina Lifford) and the family drama Broken Promises: Taking Emily Back (with Michael Krawic and Tim Ransom). In 1994 Harper was seen in the HBO crime drama Witch Hunt (alongside Clifton Collins, Jr., Christopher Darga, John Durbin, J. Patrick McCormack, and Steve Susskind). In 1995, another telefilm came about when Harper appeared in If Someone Had Known (with Randy Oglesby and Jennifer Savidge). Harper worked opposite Irene Tsu in the adult-themed telefilm Widow's Kiss(1996). That year Harper also returned to the big screen first in the FBI drama One Tough Bastard reuniting with Clifton Collins, Jr. and also series guest Jeff Kober and Neal McDonough, followed by the Navy comedy Down Periscope (starring Kelsey Grammer). Harper then reunited in 1998 with J. Patrick McCormack in the what became the most successful film of the the year, the Jerry Bruckheimer-produced, Micheal Bay-directed asteroid film Armageddon co-written by J.J. Abrams, in which Harper not only worked with McCormack but alongside many other Trek alumni (Jeff Austin, Brian Brophy, Jim Fitzpatrick, Googy Gress, Anthony Guidera, John Mahon, Matt Malloy, Andy Milder, Marshall Teague, Lawrence Tierney [in what was to be Tierney's final acting work], and Peter White). Next was 1999's true story crime film Lansky (with Francis Guinan, Peggy Jo Jacobs, Michael Krawic, Kenneth Messeroll, Robert Miano, Bert Remsen, David Selburg, and Tom Towles). That year, Harper concluded his 20th film work in the investigative drama The Insider (joined by Bruce McGill, Christopher Plummer, and Vyto Ruginis).
Ushering in Harper's 21st century resume was lending his voice to the video game Diablo 2 (2000, with Paul Eiding, Frank Gorshin, Brian George, Castulo Guerra, Nina Minton, and Ed Trotta). In 2001, Harper was seen in the flesh in Squint (with Sam Hennings and Daniel Roebuck). In 2005, Harper achieved his first short film role in Psychic Driving (with Christopher Curry). Harper's next short was 2008's A Woman in the West (with Larry Cedar and Paula Malcomson), then in 2009, Harper hit the short film triple crown acting in Into the Unknown (with Kelly Connell).
In 2010, Harper again lent his voice to a video game StarCraft II: Wings of Liberty reuniting with Paul Eiding and Armin Shimerman, and also with Michael Dorn, Robin Atkin Downes, Jason Marsden, and Debra Wilson.
1989 television guest roles
- Freddy's Nightmares episode "School Daze" (with Frank Kopyc)
- Guns of Paradise episode "A Gathering of Guns" (with Charles Napier, Ray Walston, and Time Winters)
- Dallas episode "The Leopard's Spots" (with Joey Aresco, Ron Canada, Paul Eiding, Craig Richard Nelson, and Andrew Prine)
- Beauty & the Beast episode "Though Lovers Be Lost" (starring Ron Perlman and with Edward Laurence Albert, Stephen McHattie, Armin Shimmerman, and Clement von Franckenstein)
1990s television guest roles
- Matlock episode "The Talk Show" (directed by Robert Scheerer and working with Samantha Eggar)
- L.A. Law episode "On Your Honor" (1990, starring Corbin Bernsen, Larry Drake, and Diana Muldaur, and with James Avery and Rif Hutton)
- Tour of Duty episode "Acceptable Losses" (1990, starring Dan Gauthier and with Patrick Kilpatrick)
- Quantum Leap episode "Sea Bride - June 3, 1954" (starring Scott Bakula and Dean Stockwell, with J.G. Hertzler)
- Life Goes On episode "Hello, Goodbye" (1991, starring Bill Smitrovich)
- Tequila & Bonetti episode "The Rose Cadillac" (1992, starring Charles Rocket, directed by James Whitmore, Jr., and also featuring Dennis Cockrum and Tim Russ)
- Sisters episode "The First Time" (1992, starring Ashley Judd)
- Deadly Games episode "The Trash Man" (1996, starring Christopher Lloyd with Mike Starr)
- Renegade episode "Give & Take" (1993, starring Branscombe Richmond with Patrick Massett)
- The Burning Zone series premiere (1996, starring Jeffrey Dean Morgan)
- Frasier episode "Party, Party" (1998, starring Dan Butler and Kelsey Grammer with Patrick Kerr)
- Profiler episode "Inheritance" (1999, with Bradley Pierce and Lawrence Pressman)
- Chicago Hope episode "A Goy & His Dog" (1999, with Mark L. Taylor)
2000s television guest roles
- NYPD Blue episode "Peeping Tommy" (2001, starring Gordon Clapp)
Harper was also seen as Jordan Lovell on the prime time soap General Hospital: Night Shift costarring with Ray Proscia in the late summer and early autumn of 2007.