Best happy accidents ever! <iframe width="560" height="349" src="http://www.youtube.com/embed/cTFQBHBeleE" frameborder="0" allowfullscreen></iframe>
R Lee Ermey says most of his lines in films are improvised, directors will just give him a rough overview and let him do what he wants, Se7en is another one that pops to mind.
That was a fun video but I was disappointed to not see one of my favorite ad-libbed scenes ever: <iframe width="560" height="349" src="http://www.youtube.com/embed/92IkddsjtAA" frameborder="0" allowfullscreen></iframe>
that wasnt so much an improv as it was a changing of the script. They were going to do an elaborate fight scene with the swordsman but due to illness and other delays, they were way behind schedule. During a lunch break, Spielberg was talking with Ford and other cast members about the scheduling issues and Ford chimed in and said..."well I have this gun...am I ever going to use it?". They then re-wrote the scene
The list should be comprised entirely of clips from Best in Show, Waiting for Guffman, and Spinal Tap.
Ermey was originally supposed to be just the military adviser for the film. They hired an actor to play Hartman but when Ermey tried to show the actor how the play the role, he scared the hell out of all the other actors and Kubrick decided to let him play the role himself. Most of the fear seen in the actors eyes when Ermey is in their faces is 100% real. None of them knew what he was going to say or do before he did it. The first 10 minutes of Full Metal Jacket is seriously the best opening to a film in modern cinematic history for my money.
A friend of mine's dad was a Marine in Vietnam and he said the training sequence was very realistic. The only exception was that an actual drill sergeant would know to back off when Private Lawrence was about to snap. Full Metal Jacket is still widely considered one of the most realistic war movies and Kubrick one of the best war directors.