Thomerson has had a very long career in television and in film, appearing in scores of films since the 1970s. He had a memorable minor role in Car Wash. He played Criminal Psychologist Jerry Moriarity in the 1980 slasher film Fade to Black.
Thomerson first came to prominence in the short-lived comedy science-fiction TV series Quark in 1977–78, as Gene/Jean, a character of dual gender who randomly switched from a macho to a feminine personality.
When Charles Band started up Full Moon Features in the late 1980s, one of his first projects was Trancers II (released in 1991), in which he reunited Thomerson with much of the cast from the first film. Thomerson would appear in every sequel thereafter, with the exception of Trancers 6, which instead starred Zette Sullivan in her only lead role, and used archive footage of Thomerson to enhance the story. Thomerson is considering returning in another Trancers sequel.
In 1985, Thomerson starred as the time-traveling Future cop Jack Deth in the low budget science fiction film Trancers which was produced by Charles Band and Empire Pictures. The role made him an icon of the B-movie genre, and led to Thomerson building a working relationship with the Bands. He was supposed to appear in Pulse Pounders which was ultimately never completed.
In 1986, Thomerson would reunite with a few of his Trancers co-stars for Zone Troopers, and he appeared in the vampire film Near Dark. He also appeared as a villain opposite Melanie Griffith's heroine in Cherry 2000 and as Major Dan Hackett in the Disney made-for-TV movie, The B.R.A.T. Patrol starring opposite Sean Astin, Nia Long and Brian Keith.
He appeared in NBC's 1988 television film The Incredible Hulk Returns as The Hulk's opponent, Jack LeBeau.
Thomerson has had many memorable roles in feature films, including Uncommon Valor, Air America, Volunteers, Who's Harry Crumb?, Iron Eagle, and Fear and Loathing in Las Vegas, just to name a few, as well as numerous television roles such as Tour of Duty and 21 Jump Street. He also played Colonel Savage of the Missouri Militia on The Young Riders in 1989. In the '90s he was a series regular on the television police drama Sirens followed by a regular, co-starring role on the series Land's End starring Fred Dryer.
Thomerson's most famous role is that of Jack Deth, the hero of Charles Band's Trancers series. Playing against his comedic roots, Thomerson played Deth as a hard-nosed epitome of machismo, like the science fiction equivalent of Clint Eastwood in the Dirty Harry series. The character continued in four more sequels throughout the 1990s. A fifth sequel, Trancers 6, was released in 2002 but Thomerson was not involved.
Another movie role that made Thomerson popular with fans of science-fiction was that of Brick Bardo in the 1991 film Dollman, a Dirty Harry-like alien cop who is 13 inches tall, and uses his blaster gun to take on Gangsters and devil-possessed toys in two obscure feature films. The character also appeared very briefly in Bad Channels.
Other career highlights include Babo in the adventure film Air America with Mel Gibson and Robert Downey, Jr., grimy mercenary Rhodes in Metalstorm: The Destruction of Jared-Syn, demented cult leader Lester in Cherry 2000, Loy in the horror classic Near Dark, diminutive lawman Brick Bardo in Dollman and Dollman vs. Demonic Toys, and a scruffy motorcyclist in Terry Gilliam's Fear and Loathing in Las Vegas. Thomerson is a stock player in the films of actor/director Michael Worth (DUAL, Devil on the Mountain, God's Ears) and a favorite of Director Albert Pyun (Dollman, Knights, Nemesis, Nemesis 3: Prey Harder).
