John Francis Knight III was born 26 February, 1938, in Boston., and grew up in Somerville, Massachusettes. He earned a Bachelors of Arts degree from the University of Massachusettes, and attended graduate school at the Catholic University of America.
Knight served in the Army and has done theatre. He toured with a theatre company doing Shakespeare, and appeared on Broadway.
He appeared in the films "The Long Goodbye" and "Wicked, Wicked". He had a regular supporting role in a sitcom called "Lotsa Luck" with Dom DeLuise. He also had guest roles in several other series, including "The Rockford Files", "Police Story", "CHiPs", "The Jeffersons", "B.J. and the Bear", "The Misadventures of Sheriff Lobo", "One Day at a Time", and "Diff'rent Strokes".
On Cheers he played Jack, one of the regular barflies seen in the background.,
Since appearing on Cheers, he has appeared in several films including "L.A. Confidential", "Catch Me If You Can", and "Moneyball". He has also guest-starred on television in episodes of "Trapper John, M.D.", "Knots Landing", "Magnum, P.I.", "The Nanny", "Buffy the Vampire Slayer", "JAG", "NYPD Blue", "Cold Case", and "House of Lies".
He has also done several television commercial spots, with perhaps the most prominent one being aired during the 1974 Super Bowl, as the original Meinike Muffler man.
Jack is an avid softball player, and has also toured several times with the world-famous four-man softball team, "The King and His Court".