Smith appeared in many TV series, such as Diagnosis: Murder, Star Trek: Voyager, Wings and Conan the Adventurer. In 1999, Smith had small roles as guards in Donald Petrie's My Favorite Martian and The X-Files. Smith appeared 18 times in the hit TV show Charmed, where he played Belthazor, The Source, Grimlock and Shax. 2002 also saw him appear in the hit sequel Men in Black II, where he portrayed the character Creepy. After 2002, he appeared in the TV series The O.C. and Desperate Housewives. In 2003, Smith was brother Bob (Monster Man) in the hit movie Monster Man.