Trivia

Was originally hired to play Arthur Adamson in Alfred Hitchcock's final film, Family Plot (1976), but Hitchcock had always wanted William Devane for the part. Devane was originally unavailable, so Hitchcock began filming with Thinnes in the role. When Devane became suddenly available one month into filming, Hitchcock unceremoniously fired Thinnes without explanation and replaced him with Devane (Hitchcock later claimed he was dissatisfied with Thinnes' performance). The way Hitchcock handled the firing led to a famously public confrontation between the two men in a crowded Chasen's Restaurant. Thinnes can be seen in several publicity stills from the production, but no footage apparently exists.

Best known as architect David Vincent in the 1960s cult television series, The Invaders (1967). He appeared in a mini-series remake of that series, The Invaders (1995), also in the role of David Vincent.

He made guest appearances on both of the longest running prime time dramas in US television history: Gunsmoke (1955) and Law & Order (1990).

He was considered for the role of Tom Hagen in The Godfather (1972) before Robert Duvall was cast.

Served a hitch in the US Army as a Military Policeman.

During 1967 and 1968, Thinnes starred in The Invaders, a TV series in which he portrayed an architect named David Vincent who accidentally witnessed the arrival of aliens from another planet. Vincent waged a seemingly hopeless one-man campaign against them. The series became a cult classic, leading to other 'aliens vs earthlings' films and TV shows. The Washington Post noted in 2008 that, although The Invaders "ran for just two seasons ... in 2004, TV Guide placed main character David Vincent at #6 on its 25 Greatest Sci-Fi Legends list.".

Twice Thinnes appeared on the ABC soap opera One Life to Live playing two different characters. From 1984-1985, he played the role of "Alex Crown" and from 1992-1995, he played the role of "Gen. Sloan Carpenter". During both of his stints on the show, his characters became a father-in-law to the same character, Cassie Callison.

In 2019, U.S. basic-cable network MeTV began running weekly reruns of The Invaders as part of its popular "Red-Eye Sci-Fi Saturday Night" overnight late Saturday evening/early Sunday morning sci-fi TV series programming schedule.

In 2005, Thinnes co-starred as Dr. Theophile Peyron in the movie The Eyes of Van Gogh about Vincent van Gogh (played by Alexander Barnett, who also wrote and directed) and his voluntary stay in an insane asylum. The movie focuses on Van Gogh's relationships with Dr. Peyron, as well as fellow Expressionist Paul Gauguin, and his brother, Theo.

He broke both ankles during football training at Chicago High School , He then attended Los Angles City College after which he was in the Military police in the US Army.