Knight was born in the Terryville section of Plymouth in Litchfield County, Connecticut to Polish-American parents Sophia (née Kavaleski) and Charles Walter Konopka, a bartender.

[1] He withdrew from high school to enlist in the United States Army in World War II and was a member of A Company, 296th Combat Engineer Battalion, earning five battle stars while serving in the European theatre.

He became proficient with puppets and ventriloquism, which led to steady work as a television children's show host at WJAR-TV in Providence, Rhode Island from 1950 to 1955.

He had a small part playing a police officer guarding the room where Norman Bates sat wrapped in a blanket at the end of Alfred Hitchcock's Psycho (1960).

[8] He also made guest appearances in numerous series, including How to Marry a Millionaire, Highway Patrol, Lassie, The Donna Reed Show, Peter Gunn, The Twilight Zone (in the episode "The Lonely"), Bourbon Street Beat, Death Valley Days, The Man and the Challenge, Alfred Hitchcock Presents, Mr. Lucky, One Step Beyond, Pete and Gladys, Surfside 6, Sea Hunt, The Asphalt Jungle, Dr. Kildare, General Electric Theatre, Manhunt, Cain's Hundred, The New Loretta Young Show, The Eleventh Hour, The Untouchables, Sam Benedict, The Virginian, Arrest and Trial, Ripcord, The Lieutenant, The Outer Limits (in the episode "The Invisible Enemy"), McHale's Navy, Gunsmoke, Kraft Suspense Theatre, Run for Your Life, 12 O'Clock High, Bonanza, Gomer Pyle, U.S.M.C., Combat!, T.H.E.

Knight's speaking voice also brought him work as a voice artist for various animated series produced by Filmation and Hanna-Barbera, including Star Trek: The Animated Series, The Superman/Aquaman Hour of Adventure, The Batman/Superman Hour, Journey to the Center of the Earth, Fantastic Voyage, The New Scooby-Doo Movies, Super Friends and Lassie's Rescue Rangers.

Knight's role as the vain and untalented WJM newscaster Ted Baxter on The Mary Tyler Moore Show brought widespread recognition and his greatest success.

In the Cleveland area during the early to late 1970s, a newsman simply known as "Ted" would provide news of the events at a local shopping center known as Southgate USA, often finishing the 60-second spot with a comedic flair, including wearing a jacket that resembled Baxter's blue WJM blazer.

[10] Knight's final film role was in the 1980 golf comedy Caddyshack, in which he played Judge Elihu Smails, a foil for Rodney Dangerfield's character.