When Walker, in Chris' company, switches on the TV at Brewster's house, the music you hear is the overture to Richard Wagner's "Die Meistersinger von Nürnberg"
Lee Marvin faked the recoil from the .44 Magnum when he shoots in Lynne's bed. These were in fact blanks, but afterward when shooting in Alcatraz they tried with real bullets and there was no recoil at all. Marvin said to director John Boorman, "Fiction overtakes reality".