Initial success

Thomerson entered the world of stand-up comedy in the 1970s. In Los Angeles, he became a regular at the Comedy Store and the Improv, and made numerous appearances on television variety shows and in Las Vegas.

One of Thomerson's early acting breaks came from director Robert Altman who, after seeing Thomerson's stand-up act, cast him in the film A Wedding. 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 between the two.

Feature film actor

Thomerson began a long career in television and film starting in the mid-1970s, starting with roles such as the criminal psychologist Jerry Moriarity in the slasher film Fade to Black (1980) before moving on to starring roles such as the time-traveling future cop Jack Deth in the 1985 low-budget science-fiction film Trancers, his most famous role.

In 1986, Thomerson reunited with a few of his Trancers co-stars for the World War II science fiction film Zone Troopers; he also appeared in the vampire film Near Dark, and played a villain opposite Melanie Griffith's heroine in the science fiction film Cherry 2000. He also appeared in NBC's television film The Incredible Hulk Returns (1988) as the Hulk's opponent, Jack LeBeau.

When Charles Band started Full Moon Features in the late 1980s, one of his first projects was the sequel Trancers II (1991), in which he reunited Thomerson with much of the cast from the first film. Thomerson would later appear in each of the sequels except Trancers 6.

Another film role making Thomerson popular with science fiction fans was that of Brick Bardo in Dollman (1991), a Dirty Harry-like alien cop who is only 13 inches (33 cm) tall; the character also appeared briefly in Bad Channels.

In the 1990s, he was a series regular on the TV police drama Sirens, followed by a regular, co-starring role on the series Land's End.

Video games