A replacement had to be found for Manis the Orangutan, the original Clyde, as he had grown too much in the two years since the first movie.
One of Clint Eastwood's most successful movies. So was its predecessor, Pendenciero rebelde (1978). Both, when adjusted for inflation into constant dollars, are still big box-office titles, this movie being ranked in the Top 200 grossing movies of all-time.
In this movie and included on the soundtrack, Clint Eastwood sang a duet with the legendary Ray Charles, titled "Beers to You".
Per Sondra Locke's autobiography, Clint Eastwood took megadoses of vitamins and ate boiled potatoes like popcorn to bulk up for his role as a street boxer.
The production company at first wanted to use the Wyoming Highway Patrol car and their uniforms for the scene when the motorcycle gang first arrives in Wyoming, but the state refused. The Teton County Sheriff's office was quick to offer its car and uniforms for the shot. The Jackson Hole Police Department car at the barn is also the department's actual car on loan, as are the uniforms. The cops, however, are actors.