Greenberg had a recurring role as Mr. Loopman in the FOX television series Parker Lewis Can't Lose, on which fellow Voyager guest star Gerrit Graham was a regular. Greenberg had previously appeared with Graham in the 1986 Roger Corman-produced horror film Chopping Mall, co-starring Dick Miller. Greenberg also had roles in the films Cocktail (1988, starring Laurence Luckinbill) and Guncrazy (1992, featuring Tracey Walter) and made a guest appearance in a 1993 episode of Beverly Hills, 90210, with Ann H. Gillespie.