'Barry McGuire' (Old Wrangler) made his own flowered pants for the movie. During that time they were quite the rage.
A not-so secret fact is that the FBR and CEA were originally identified by their real names; apparently pressure was brought to rename them after the film was shot. Thus every line where FBR or CEA is spoken has been redubbed, often very audibly. If you watch actor's lips, they're really saying FBI and CIA.
According to Larry Karaszewski of the website trailersfromhell.com, Flicker said the monologue on the n-word was based on a true story told to him by Diana Sands.
CEA agent Don Masters (Godfrey Cambridge) wears a "Dizzy Gillespie for President" sweatshirt at the beginning of the movie. Legendary jazz trumpeter Dizzy Gillespie actually ran a short-lived campaign for the office in 1964 which, while not entirely serious, appealed to many disaffected voters.
During the filming of this movie on the lower west side of NYC James Coburn was being chased by two fellow actors who were dressed as uniformed cops. Shouting "Stop Stop", they chased Coburn around a corner and into a real on-duty uniformed NYC police officer. The officer dropped Coburn with one blow from his nightstick. Coburn had to seek medical treatment which subsequently stopped the filming for a time.
The head of the "FBR" is named Lux. "Lux" was a then-popular brand of vacuum cleaner. At the time, the director of the FBI was named Hoover.
The name of the ship in the movie is the "Mata Hari" (named for the famous spy).
The San Franciscan band The Grateful Dead were asked to be in this film. They would have been a rock band that Dr. Schaefer winds up hanging out with. Unfortunately the band wanted complete control over that scene.
The subtitle option on the DVD translates the spoken Russian (between Kropotkin and his superior, and later with Masters greeting his old friend) into English.