Worked with the Black Panthers in the 1960s.
Besides his own appearances in the Star Trek series, his ex-wife Julie Cobb played "Yeoman Thompson" in "Star Trek: By Any Other Name (#2.22)" (1968) and his ex-stepdaughter Rosemary Morgan played "Piri" in "Star Trek: Voyager: The Chute (#3.3)" (1996).
At 6' 7", he is the tallest Oscar-nominated actor of all time (he was nominated for his Best Actor in a Supporting Role in Babe (1995)).
He is the only actor to ever utter the words "Star Trek" on Star Trek itself. In the movie Star Trek: First Contact (1996), his character Zefram Cochrane said to the crew, "...and you're all astronauts, on some kind of...star trek?".
In The People vs. Larry Flynt (1996), he plays Charles Keating, a publisher. Keating has the same first and last initials (CK) as Charles Kane, the character in Orson Welles' Citizen Kane (1941). In that movie, Charles (Foster) Kane is a newspaper publisher based, in no small part, upon real-life newspaper magnate William Randolph Hearst. Cromwell portrayed Hearst in the behind-the-scenes look at "Citizen Kane", entitled RKO 281 (1999) (TV).
Was ranked 56 of Total Film's Top 100 Greatest Movie Villains for his role as Captain Dudley Smith in L.A. Confidential (1997).
Has twice played a prison warden, both with units of measure in the title: The Green Mile (1999) and The Longest Yard (2005).
Celebrity sponsor of the Great American Meatout, March 20, 2001.
Was arrested for trespassing during an animal rights demonstration in Virginia, targeting the Wendy's fast food chain. He and four other PETA protesters refused to leave after urging patrons to boycott the restaurant. Cromwell was released on his own recognizance after about five hours. [3 July 2001]
Played a US President four times - fictional President Fowler in The Sum of All Fears (2002) fictional President Newman in "The West Wing" (1999), Lyndon Johnson in the telemovie RFK (2002) (TV), and George H.W. Bush in Oliver Stone's film W. (2008/I).
Played a fictional President in The Sum of All Fears (2002) and real-life President Lyndon Johnson. Donald Moffat, who has also played Johnson, played the fictional President in Clear and Present Danger (1994).
Stars in the remake of 'Salem's Lot (2004) (TV), based on Stephen King 's novel, and his wife, Julie Cobb, starred in the original 1979 version.
Was given the role of the Prison Warden in The Longest Yard (2005) after negotiations with Gary Oldman fell through.
In addition to having played four United States Presidents, he appears in The Queen (2006) as Prince Philip, the husband of Queen Elizabeth II.
After focusing for decades on film and television, Cromwell returned to the stage in March 2012, after an absence of 13 years, in the role of Pozzo in Samuel Beckett's "Waiting for Godot" at the Los Angeles Mark Taper Forum. Prior to that, he appeared in the Tom Stoppard play "The Invention of Love" at ACT in 1999.