- Acting for Two: In addition to the role of Billy the Kid, Emilio Estevez dressed up as one of the enemy combatants in the McSween shootout at the end.
- Deleted Scene: In the DVD Commentary Casey Siemaszko reveals the prostitute Charlie goes to see was actually a longer scene, and the end of the scene he tells the guys the woman was his mother.
- Enforced Method Acting: Lou Diamond Phillips is afraid of heights. That's why he moves so slowly on the 30-foot high cliff.
- Fake Irish: Jack Palance as Lawrence Murphy.
- Fake Nationality: The Mexican-Navajo Chavez was played by Lou Diamond Phillips, who is of Filipino, Spanish, and Cherokee descent.
- Irony as She Is Cast: Charlie Sheen was reportedly a terrible horse rider. Throughout the shoot he couldn't keep his balance on the horse and fell off several times. After the shoot out with Henry Hill, his horse took off and he had no clue how to make it stop.
- Real-Life Relative:
- What Could Have Been:
- The movie accounts for one of the very few James Horner scores to be thrown out and unused. Westerns don't seem to have his ideal genre (The Missing wound up ending his working relationship with Ron Howard).
- In a 2016 meet and greet interview with Lou Diamond Phillips, he revealed that Sean Penn was originally offered the role of Billy and Patrick Swayze was offered the role Dick Brewer. Due legal troubles at the time Penn wasn't able to accept the role. Swayze wasn't interested in doing an ensemble movie and he had done several movies with the Brat Pack and he was trying to get away from that.
- Writing by the Seat of Your Pants:
- In the scene where Billy is having Doc write a letter to the Governor, Emilio Estevez wanted to make it look like he was making the speech off the top of his head, so the crew made a cue card for him to read. If you look closely, you can actually see his eyes moving while he is reciting the speech.
- None of the movie's fight scenes were choreographed. The actors just improvised.
Trivia / Young Guns