Lopez began acting in 1984 when he appeared as younger brother Tomás in the short-lived ABC comedy series "a.k.a. Pablo". That same year, he was cast as a drummer and dancer on "Kids Incorporated" from three seasons. In March 1987, he was cast as a guest star on the sitcom "The Golden Girls" as a Latino boy named Mario who faces deportation. He was cast in a small part in the movie "Colors" (1988) as Felipe's friend. In 1989, Lopez was cast as A.C. Slater in the television Saturday-morning series sitcom "Saved by the Bell" (1989–1993), and its spinoff "" (1993–1994), a role which lasted five years.