Bill Cosby made three appearances, all in the first season, as Cliff Huxtable from The Cosby Show. Cliff is only seen in the Huxtable living room or kitchen on the other end of phone calls from Denise. Cliff's only appearance on the Hillman campus was seen in the Cosby Show episode which served as an introduction to A Different World.
Waiter, check please.
Whitley Marion Gilbert Wayne: Yes, la cuenta and *fast*!
Julian Day: It's "il conto".
Whitley Marion Gilbert Wayne: Oh, cuenta, conto, Kunta Kinte, just get the ding-dang check!
Throughout the course of the series, Whitley's talents go back and forth between being an accomplished singer/dancer and having little to no singing/dancing skills at all.