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When Baby mentions "monks burning themselves in protest" at the beginning of the film, she refers to the day a Buddhist monk (Thích Quang Ducset) set himself on fire in Saigon in a ritual suicide to protest government anti-Buddhist policies. Therefore we can assume the action started after June 11, 1963, when this occurred.
Patrick Swayze had to convince Jennifer Grey to be in this film because she disliked him so much while filming Red Dawn (1984).
Patrick Swayze was offered $6 million to reprise Johnny for a sequel. Swayze wasn't a fan of sequels and turned it down.
The dancing that Patrick Swayze and Jennifer Grey do during the love scene was the same dance that they did for the screentests. It was not originally supposed to be in the film.
Patrick Swayze insisted on doing his stunts. During the log scene, he kept on falling off the log and injured his knee so badly he had to have fluid drained from the swelling.