Character actor John Petlock's relatively short career was marked by steady work in a range of TV and film projects, with his most notable role coming in the popular drama "Dallas". Petlock appeared in a handful of TV shows when he was cast in a recurring part on the popular nighttime soap "Dallas" in 1978, playing Dan Marsh in a story arc that spanned several episodes of the show's inaugural season. While the role on the high-profile show didn't lead to many other significant parts, he worked consistently for the next two decades. He had multiple appearances on Will Smith's "The Fresh Prince of Bel-Air" and could be seen on five episodes of the sitcom "Family Ties", including the 1982 pilot. TV movie roles came in an "ABC Afterschool Special", the Ricky Schroder drama "Two Kinds of Love", and the Barry Manilow musical vehicle "Copacabana". He played a pathologist in the true-crime miniseries "The Atlanta Child Murders" and appeared in the Emmy-winning "Baby M" in 1988, also based on a true story. One of his few feature roles came in the medical-school drama "Gross Anatomy", playing an interviewing professor. In the 1990s, he continued playing guest parts on television, with his last role coming in the criminal drama "The Practice" in 1998.