- Creator Cameo: The whistling bounty hunter is voiced by Sergio Leone.
- Deleted Scene: Early American and British VHS releases and TV broadcasts feature an extended version of the scene where El Indio tortures Mortimer and Manco, including some new dialogue:
Mook: Why let them live?
El Indio: All things at the right time.
- Playing Against Type: This, any several other spaghettis such as Sabata, is one of the few times, besides, say, Escape from New York, that you'll ever see Lee Van Cleef play a heroic character of any type.
- Playing Gertrude: Col. Mortimer is said to be almost fifty, yet Lee Van Cleef was only forty at the time.
- What Could Have Been: Lee Marvin, Henry Fonda, Charles Bronson and Jack Palance were originally considered for the role of Colonel Mortimer.
- You Look Familiar
- Lee Van Cleef played the Bounty Hunter Colonel Douglas Mortimer, who worked as the protagonist's ally. Van Cleef later plays the villain Angel Eyes in The Good, the Bad and the Ugly.
- El Indio's actor, Gian Volonte, also played Ramon, the villain in A Fistful of Dollars. It can be somewhat jarring if you watch the two movies back to back. It could have been worse: Volonte was originally supposed to play Tuco in The Good, the Bad and the Ugly as well, but Leone later decided he wanted an actor with a natural comical talent.
- Also Luigi Pistilli, who played Groggy in this film, and Tuco's brother in The Good, the Bad and the Ugly.
- Mario Brega as Nino, who played Chico in A Fistful of Dollars and would go onto play Corporal Wallace in The Good, the Bad and the Ugly.