"Christ it was supposed to be a fun film and Steiger is far far from having a sense of humor" Henry Hathaway said about his star Rod Steiger.
A fifteen ton actual safe was used for the heist sequence. Rod Steiger and Michael Dante actually cracked the safe for the shooting, advised by technicians from the vault's manufacturer.
Richard Widmark, Anne Bancroft, and Fredric March were originally offered the lead roles, and subsequently Stewart Granger and Jean Simmons were sought to headline the film.