Character mistake: In the opening scene is a paragraph describing why the Top Gun school was started. The word "insure" is used when the word should have been "ensure". They wanted to guarantee the U.S. had superior pilots, not take out an insurance policy.
Character mistake: When Doug Masters approaches his aircraft at the airfield before racing 'The Snake', Col Sinclair has a right hand access panel open on Doug's Cessna 150 upper engine cowling and is allegedly working on the fuel system saying "As lean as you were runnin', if it went into a stall, you woulda lost your engine, and would never been able to pull it out." The carburetor, gascolator, throttle linkage and carburetor control lines are on the bottom of the engine (Continental O-200). The panel he closes after sticking bubble gum on accesses the battery, the right hand magneto and the oil dipstick. Not only did Col Sinclair not do what he said he said he did without a sign-off in the aircraft's logbook, it would be totally unnecessary, as aviation updraft carburetors use a cockpit or engine controlled fuel mixture control that would have simply been left in 'full rich' position after engine start for the altitudes the aircraft would have been flying. And stalling is an aerodynamic condition of angle of attack being exceeded or insufficient airflow over flight surfaces, not fuel starvation, which is the condition being addressed. (00:11:30 - 00:12:30)
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.
Character mistake: Both in the movie (and stage) versions, Mushnik makes a verbal mistake. Seymour shows Mushnik his new plant (Audrey II) for the very first time, but seconds later when the plant suddenly droops, Mushnik asks Seymour, "Why is it always wilting like that?" Always? He's just seen the plant! The line should be, "Why is it wilting like that?" Some smart stage directors of the play version have wised up and changed the line.
Character mistake: When the undercover cop says, "Hi, when was the last time you had a good..." she doesn't identify herself as a police officer. (00:37:15)
Character mistake: When William finds the footprints on the ground after the body is found in the blood vat, he tells Adso that they were twice as deep as they should've been because the person who made them was weighed down by the weight of a body. Adso points out that the footprints were going away from the vats, to which William rebukes him and says that the man who made the prints was possibly dragging the body. If that was so, the footprints would not have been so deep, as the person moving the body would not have been weighed down nearly as much by dragging one along the ground. William is a learned investigator who shouldn't have made such an obvious mistake.
Character mistake: When Brenda first witnesses Connor and the Kurgan fight, Kurgan says "I am the only one." Afterwards, Brenda asks "What does he mean by there can be only one?" She somehow misheard Kurgan and thought he said the movie's iconic catch phrase.