Mud thrown at the window at beginning of film moves and disappears.
The film depicts the filming of Hud taking place after the death of Olivia. In actuality, Hud was finished filming by August of 1962 and Olivia did not die until November.
Both lead actors used the phrase 'Shit happens' during the film. The term was not in existence in 1963, only becoming common in the 1980's, with Wikipedia citing the first recorded reference being in 1964.
Neal's American accent comes and goes.