A few weeks before filming started, Balthazar Getty fell from a tree and broke both his wrists. The director decided to write his injuries into the script, and put his character Ralph's arm in a sling for half of the film.
Sam and Eric (the twins) are never identified by their names throughout the film. Even the official cast list enters them as the Twins . This points out their interchangeability since even in the book (and the original 1963 film) no one could tell them apart .