Revealing mistake: Several maps of Europe shown in the film have Germany divided into East and West, and show national borders from 1945 onwards.
Revealing mistake: Near the end of the film, there is a football game played between the rival MASH units. Although the game is supposed to be taking place in a remote location of Korea in 1951, late model 1960's automobiles can be seen driving on a nearby highway as the game progresses. This gave away the fact that the football scenes were shot at a university in Southern California.
Revealing mistake: Blank firing adaptors are visible on the bow machine guns of Oddball's Shermans as they shoot up the rail yard. (01:00:05)
Revealing mistake: The cannons shown are firing blank charges, which produce no recoil. Recoil has been simulated by towing the guns backwards when they fire. The problem is, there is always a distinct delay between the discharge and the "recoil." The cannon also seem to largely fire explosive shells. At no point do we actually see a cannon ball rolling or bouncing along the ground or into any group of soldiers.
Revealing mistake: When the mayor's wife attempts suicide by stuffing herself with pills, she is lying behind a sofa, only her arm and the pill bottle being visible as she pours the contents into her mouth. In the next shot (a close-up), however, the crown of her head is visible, and it is evident that she pours the pills over the top of her head.
Revealing mistake: During the Little Bighorn massacre one of Custer's lieutenants turns to address Custer and is struck in the back with an arrow, and the thick pad or board is visible under the actor's shirt.
Revealing mistake: During the Flak attack on the B25s Arfy notices Orr's plane going down. The scene cuts to a smoking plane going down at a steep angle, but you can see the plane was flying straight and the film turned at an angle as the colors on the horizon are also at a steep angle.
Revealing mistake: After Clint has shot the 3 would-be rapists, he is rifling through the pockets of the dead men. As he checks the pockets of the first guy he shot the "dead" guy in the background is breathing.