Sylvester Stallone hated the first cut of the film so much that he tried to buy the film back and destroy it. When he couldn't do that, he suggested that the producers cut much of his part and let the rest of the characters tell the story. That cut the movie time in half and set a precedent for future action movies.
A scene was filmed but never used where Rambo, while in the cave after dispatching Teasle and his men, has another flashback: he and his buddies are in a bar in Vietnam, being entertained by the local women. Rambo takes one to a back room and they make love. The scene then flashes to the present, and Rambo begins to cry.
(At 1:03.41) When Rambo is believed to have been killed in mine attack by the National Guardsmen, Teasle returns to his office. Behind him, you can clearly see a display case that displays three medals. The three medals, from right to left, are: the Silver Star, The Purple Heart, and the Army Distinguished Service Cross Medals. These indicate Teasle was a highly decorated Korean War hero as both the Silver Star and ADSC are awarded for extreme valor and bravery in enemy combat. The subtext of the book was a battle of different war tactics, for this reason; this is underplayed in the film.
The large piece of rotten canvas that Rambo finds in the woods and cuts into a makeshift coat, was in fact not a movie prop, but a real piece of rotten canvas found by the film crew during the movie's production. Since there was only one piece, Sylvester Stallone joked about how the canvas became a treasured prop on the set. After filming ended, Stallone kept the rotten canvas and still has it in his possession to this very day.
In the DVD commentary, Sylvester Stallone compares Rambo to the monster of Dr. Frankenstein and Col. Trautman as the doctor, in the respect that Rambo is a war machine monster created by America to do its bidding, but then he escapes and runs amok, but also wanting to fit into a society who shuns him, and Col. Trautman basically was instrumental in making Rambo into what he is and feels remorse for how he turned out and does what he can to help make things right.
It is often claimed that in Japanese, "rambo" means "violence". This is not quite correct. The adjective "ranbou" or "rambô" (depending on how you choose to romanize it) has a meaning closer to "rowdy", although it can quite legitimately be translated as "violent". It is also identical in pronunciation to the Japanese title of the film.
During the scene when Rambo, on the stolen motorcycle, is being chased by the police, the stuntman representing Sheriff Teasel who was driving the patrol car (Bennie E. Dobbins) suffered a broken back (a compression lumbar fracture) as a result of a seventy mile per hour first take that launched the car to a remarkable height on the ramp assisted steep approach to the railway crossing. The vehicle slammed down flat on its chassis, causing the injury to Dobbins, and it rolled several hundred feet further up the road before coming to a stop. When Dobbins opened the door to exit he found himself unable to walk and he fell to the ground. This original high jump and landing was re-shot and replaced in the final cut, with a more modest and believable car jump and landing, using a different car (and stunt driver).
After the success of Convoy (1978), Kris Kristofferson was considered as a possible choice for John Rambo. Some felt the former Airborne Ranger would make a solid Rambo, and they hoped his good friend Sam Peckinpah could be persuaded to direct.
According to Sylvester Stallone in the DVD commentary, the names of the people on Rambo's team in Vietnam (as read by Col. Trautman) are actually names of various people of the film's crew, including make-up artist Michael Westmore and costume designer Tom Bronson.
In spite of the fact that the air and water temperatures during filming were extremely cold, and he wore only a tank top during most of the movie, Sylvester Stallone did not get sick, until someone offered him a shot of brandy.
With the exception of the National Guardsman leader Lt. Clinton Morgen (Patrick Stack), all of the other guardsmen who pursue Rambo into the mineshaft are referred to by the same names as the actors who portray them.
In the DVD commentary for the film Sylvester Stallone recalls an incident during filming where a girl in the town bar pretended to be a fan of his in order to try and wheedle a free round of drinks out of him. He later includes just such a scene in his film Rocky Balboa (2006).
Currently, TV rights to this film are owned by Paramount Pictures, which acquired Spelling Entertainment, the previous TV right-holders, in 1999. The prints of the film that air on Spike, however, open with the Paramount logo variant that has the Paramount Communications (formerly Gulf+Western) byline, despite the fact that Paramount didn't get TV rights to the film until years after the studio was sold to Viacom (the Paramount/Viacom merger completed in 1994, while the Spelling/Viacom merger completed in 1999).
A plot point that was present in the novel but absent from the film was the primary reason behind Teasle's resentment and contempt towards Rambo, which was that Rambo was a veteran of the Vietnam War, which gained a lot of attention, whereas Teasle was a veteran of the Korean War; a war which most people had all-but-completely-forgotten at this point in time.
In his commentary for First Blood author David Morell cites the inspiration for John Rambo as being World War 2 hero and later Hollywood actor Audie Murphy. In 'Rambo' the final film of the series the character's last stand in the finale is very similar to how Murphy won the Congressional Medal of Honour, manning a vehicle mounted 50. calibre machine and singlehandedly holding off hundreds of enemy soldiers.
Kirk Douglas was originally cast to play Colonel Samuel Trautman. Because of script issues (Kirk wanted Rambo to die at the end, as in the novel), he dropped out of the film and Richard Crenna was cast at the last second.
The end of the chase between Rambo (on a motorcycle) and Sheriff Teasle, where Teasle's police car rolls off an embankment and flips over upside down, was not scripted this way, but when the car ended up in that position, director Ted Kotcheff liked the result so much that he continued shooting the scene and had Brian Dennehy get into the police car while it was still upside down, and filmed the scene as it appears in the movie.
Sylvester Stallone suffered several serious injuries during filming of this movie. For the scene where Rambo jumps off the cliff and injures himself on some tree branches on the way down, Stallone performs the stunt himself during the bottom third of the fall, and in the process, broke one of his ribs when he landed on the tree branch. Stallone remarks on the DVD commentary that it was easy to play the landing when Rambo screams in pain, since he was not acting and was really in pain. Also for the scene where Rambo first runs into the abandoned mine shaft to elude the guardsmen firing at him, Stallone places his hand on top of a piece of wood, not realizing that his hand was right on top of a gunfire squib that went off a second later, injuring his hand in the process. Stallone mentions that the pain he felt was so intense, he was afraid to look at his hand, fearing the squib had completely blown his thumb off.