Sylvester is best known for his role on the TV series Married... with Children as Griff, the co-worker and friend of Al Bundy at the shoe store. Harold's other TV roles include the miniseries Wheels (1978), the short-lived 1981 series Walking Tall, Today's F.B.I., Mary (1985), Shaky Ground, and "A Different World". The most recent TV show in which he starred was The Army Show. Sylvester had a recurring role on the TV series City of Angels. He has made guest appearances on shows, ranging from The Eddie Capra Mysteries to Hill Street Blues to Murder, She Wrote to NYPD Blue.