Shirley MacLaine did not get along during the shoot with director Don Siegel, with whom she openly fought.
Hogan (Clint Eastwood) has on the same gun belt and holster that Eastwood as "The Man with No Name" wore in the "Dollars" trilogy (the three Spaghetti Western movies directed by Sergio Leone).
Shirley MacLaine gets top billing in the credits (both opening and closing). This was the last time Clint Eastwood received second billing - or anything less than first - until A Perfect World (1993), and the only time his leading lady was played by an A-list star until The Bridges of Madison County (1995).
Director Don Siegel said producer Marty Rackin wanted to save every dollar on the shooting of this movie, and they disagreed on many points. According to Siegel, Rackin used totally unknown and cheap Mexican actors instead of well-known supporting American ones.