According to Larry Bishop, Richard Pryor pulled a prank in which he came to the set naked and shocked Shelley Winters.
Max Frost (Christopher Jones) asks Billy Cage (Kevin Coughlin) how long he thinks he is going to live and he replies, "Thirty, man." Ironically, in real life Coughlin was killed in a hit-and-run accident on January 19, 1976, only five weeks after his 30th birthday.
The song "Shape of Things to Come", written by Barry Mann and Cynthia Weil, was a number 22 chart hit for Max Frost and the Troopers (a "studio group" made up of session musicians) in 1968. In 2006, it was featured in commercials for the Target Corporation.
American International Pictures originally offered the role of Max Frost in the film to noted folk singer-songwriter Phil Ochs, who was known at the time to want to branch out into film work; however, after reading the screenplay, Ochs turned it down, saying that the story presented the youth counterculture of the 1960s in a badly distorted light.
In the film, on November 5, 1968, the Republican nominee Max Frost is elected President of the United States, defeating the Democratic incumbent Lyndon B. Johnson. He is inaugurated as the 37th President on January 20, 1969. In reality, former Republican Vice President Richard Nixon won the 1968 election, defeating the Democratic incumbent Vice President Hubert H. Humphrey. At the time of filming, it was widely expected that Johnson would run for a second full term in 1968; however, on March 31, 1968, he announced that he did not intend to do so.