Continuity mistake: When Jim Garrison goes to Angola Prison to interview Willy O'Keefe, Willy tells of a time before the assassination of JFK where he was alone with David Ferrie, Lee Harvey Oswald, Clay Shaw, and two Cubans. When we see the flashback, there are a total of six Cubans in the room, not two. (00:50:05)
Suggested correction: The implication is that Willy is lying or misremembering facts.
Continuity mistake: At one point during the meeting between Kevin Costner and John Candy, Candy bolts out of his chair and the sunglasses he was wearing fall off. In the next cut Candy is wearing them again without having picked them up. [This scene is edited from a longer scene (that is included on Disc 2 of the JFK "Oliver Stone Collection" DVD). In that sequence, Candy sits down and puts his sunglasses back on. Still a mistake, though, but there's why.]
Suggested correction: When Dean stands up, his sunglasses are in his right hand. So he did pick them up.