Captain America's (Peter Fonda's) chopper was so "squirrely" to ride that at one point Jack Nicholson (who was on the back) squeezed his knees on Fonda's side to balance himself and broke one of Fonda's ribs.
During Jack Nicholson's "UFO" speech, Dennis Hopper was intent on getting him very stoned on marijuana. The laughing that eventually broke up his speech was not planned, and when Nicholson repeats the line "it . . . it . . . would be devastating . . . " it was the next take.
For the famous soliloquy that Peter Fonda does in the cemetery while tripped on acid, Director Dennis Hopper asked Peter to talk to the statue as if he were talking to his mother, who died a suicide when Peter was 10 years old. Peter didn't want to do it, as he had never confronted his feelings about his mother. But Hopper insisted, which is why you hear Peter call the statue "Mother", and he states that he both loves her and hates her, which expresses his conflicted emotions. This scene persuaded Bob Dylan to allow the use of his song "It's Alright Ma" in one of the final scenes, which contains lyrics referencing suicide. Peter told Dylan, "I need to hear those words", and he agreed to its use.
In 2007, the American Film Institute ranked this as the #84 Greatest Movie of All Time.
It was one of the first films to make extensive use of previously released musical tracks rather than a specially written film score. This is common with films now but was quite unusual at the time (the exception being The Beatles films and some other special cases).
Some graffiti on the wall of the jail cell reads "H D Stanton", likely a reference to Harry Dean Stanton, a good friend of Jack Nicholson.
Some of the film was shot on 16mm film instead of 35mm. This was demo footage shot a year before production began.
Some of the weird lighting effects in the LSD scene came about because a can of film was accidentally exposed when it was opened before being developed.
The 1962 1200 cc Harley's driven by the main characters in the film were actually purchased from the Los Angeles Police department. Harley-Davidson refused to provide free bikes for the film because "The protagonist were outlaws and they thought it was bad for their image." according to an article that appeared in the June 2005 edition of the History Channel magazine.
The Captain America jacket was designed by Peter Fonda and made by "two little old ladies" in Los Angeles. It was later sold at a charity auction.
The final campfire scene was left out of the original shooting schedule and was shot after both motorcycles had been stolen.
The New Orleans cemetery is St. Louis #1, a Catholic cemetery. They didn't have permission to shoot there and Catholic audience members were shocked that the church had allowed it. Since then no other films have been allowed to shoot at St. Louis #1, unless it's a documentary and you have permission. Interview with the Vampire: The Vampire Chronicles, Double Jeopardy and other films since then have all used the Lafayette Cemetery, which is Protestant.
The original title of the film was "The Loners".
The rednecks in the Louisiana coffee shop who taunt the boys, and the two in the pickup truck at the end of the movie, were all local residents recruited by the filmmakers. In the case of the coffee shop denizens, the filmmakers were preparing to audition a group of local theater people when Dennis Hopper saw Buddy Causey Jr., Duffy Lafont and several others watching them and making wisecracks and decided to use them instead.
The sign on the wall, 'Death only closes a man's reputation and determines it as good or bad," is a quote from 'The Works of the Right Honourable Joseph Addison, volume 4'.
The swimming scene (Billy and Wyatt go swimming with two commune girls) was shot at two different times. When they shot the scene Peter Fonda was in the hospital. You can't see him together with Dennis Hopper or one of the girls in the entire scene. The legs you see are from a stand-in. The images of Fonda were shot separately, weeks later.
There is a quote from François-Marie Arouet better known by the pen name Voltaire, "If God didn't exist it, it would be necessary to invent him."
There were 2 bikes used for Captain America, one was stolen the other was burned in the end of the movie. The burned bike was later restored by Peter Fonda and was sold to John Parham and can be seen in the National Motorcycle Museum in Anamosa Iowa.