But Guy was virtually unknown when she won the role of Whitley Gilbert, the rich girl, African American Southern belle on "A Different World", the spin-off from NBC's successful sitcom "The Cosby Show". The show was supposed to be a vehicle for Lisa Bonet, but when the series sputtered in its first season, Bonet was removed from the cast and Guy was awarded top billing and the focus of the show. During the course of the sitcom's run, her character went through many changes, was mellowed, eventually married and gained a social consciousness. Although Guy had first worked in longform TV in a bit as a bank teller in the 1987 CBS miniseries "At Mother's Request", she headlined for the first time with "A Killer Among Us" (NBC, 1990), about a juror who suspects that the foreman of her panel is the true murderer in the case, and convinces the police of such--although she ultimately turns out to be wrong. Guy also was among the four stars of "Stompin' At the Savoy" (CBS, 1992), about young women from the South working as domestics by day and enjoying Harlem by night and had a key role in "Queenie" (CBS, 1993), drawn from Alex Haley's story of his paternal grandmother. In early 1995, Guy did a short guest-starring sting on "Melrose Place" (Fox), as Caitlin Mills, a bitchy whirlwind who could take Amanda (Heather Locklear) on and--almost--win.
Guy's feature film path did not develop as rapidly as her TV stardom. She was one of the "wannabe" students in Spike Lee's "School Daze" (1988), and the vixen slain while in bed with Eddie Murphy in "Harlem Nights" (1989). Guy also recorded an album in 1990 as well as several music videos, which proved popular. In the late 90s, she found renewed success on stage, appearing in the Broadway and touring production of "Grease" and headlining the national tour of Kander and Ebb's "Chicago".