Akira Kurosawa told Toshirô Mifune that his character was like a wolf or a dog and told Tatsuya Nakadai that his character was like a snake. Inspired by this direction, Mifune came up with Sanjuro's trademark shoulder twitch, similar to the way a dog or wolf tries to get off fleas.
Sergio Leone was inspired by this film and made the famous "spaghetti western" Für eine Handvoll Dollar (1964) with a similar plot. However, because Leone did not officially get permission to remake this film, which was copyrighted, Akira Kurosawa sued him and delayed the release for three years. Leone paid him a sum plus 15% of the profits. Interestingly enough, Kurosawa himself stated that he based his movie on Der gläserne Schlüssel (1942), an adaptation of Dashiell Hammett's novel, without officially crediting either source. However, various critics and readers of Hammett's work have noted that Yojimbo's overall plot is closer to Hammett's "Red Harvest" and not "The Glass Key."
Although the most common meaning of the word "Yôjinbô" is "bodyguard", the etymological origin of the characters (kanji) meant a stick or pole used for self-defense. Depending on the context, it can also mean a "bar" (e.g. on a door) or a "bolt", or instead of bodyguard, it can mean "security", "guard" or "watchman", always in the sense of "protector".
Akira Kurosawa asked his sound engineer Ichirô Minawa to come up with a sound effect to be used when a sword is cutting, and killing, someone. After testing out slicing a sword into beef and pork, he finally found the perfect sample: putting two wooden chopsticks inside a raw chicken, then hacking it with a sword.
Masaru Sato was instructed by Akira Kurosawa to write "whatever you like" so long as it was not the usual period samurai film music so commonly used by all the major studios at the time. He ended up writing something that was inspired by one of his idols, Henry Mancini, whom he had the pleasure of meeting shortly after the film was released, where they discussed his "Yojimbo" soundtrack.
Akira Kurosawa: [weather] Like in most Kurosawa films, rainy weather is present in a few scenes, increasing the effect of the characters' discomfort. The windy weather all throughout the film represents the chaotic life in the town.