Continuity mistake: In the very beginning when the transport plane carrying Taylor and the other replacements arrive, the propellers on the plane are not moving and it appears it's being towed. An army truck drives in front of the plane, momentarily blocking the view of the plane, and the propellers are spinning as soon as the truck passes.
Character mistake: When the soldiers are emtying the latrines and the "surfer" guy says he "broke a hundred the other day" and has 92 days left, he states that April 17th is his DEROS (Date Eligible to Return from Overseas). Later we hear Charlie Sheen say that it's "New Years Day." This would have put the "Latrine scene" around January 5th.
Revealing mistake: In the scene after the final battle, where Charlie Sheen is walking up on the crawling figure of Tom Berenger. In the shot of Tom Berenger crawling, you can see two electrical cords with white tape coming from Berenger's left leg as he is crawling, obviously used for the squibs when he is shot by Sheen. (01:44:30)
Other mistake: In the scene where the Heads are smoking marijuana in their clubhouse, Sgt. Elias cocks his shotgun and tells Pvt. Taylor to put his mouth to the barrel. Elias puts his mouth to the breach and blows smoke into Taylor's mouth. When the shotgun was cocked, it opened and closed the breech. Elias couldn't have blown smoke through a closed breech.
Continuity mistake: After the last battle, a character stabs himself in his right leg in order to get a medical discharge. When they show him on the helicopter leaving, his left leg is bandaged, and his right leg has no bandage.
Continuity mistake: When the Platoon arrive at the church, Elias wears a black headband. While he is running in the jungle gunning down a couple of Vietcong he is wearing a camouflage headband, when Barnes is about to betray him, he mysteriously then is wearing a headband that says "air born" after that in his famous death scene, he wears a green headband.