The 1987 Stanley Kubrick film Full Metal Jacket, is a jarring look at war and the duality of what lies in a man's heart. This film holds what it believes to be the essence of what a man is as a constant and tries in many ways to get that across. One of the first, are the actions of Private Gomer Pyle. Specifically, his decline and ultimate destruction. Full Metal Jacket offers the most in-depth look at this character and Private Joker and are granted more transparency than most others. This film attempts to act as a polarizing look at war and the condition of man.
Pyle, is initially shown to be a happy-go-lucky dullard. He moves through the first portion of the movie with a slack-jawed grin that works as one of the triggers for Gunnery Sergeant Hartman. This would have been a non-issue, if not for the mental decline that he faces later in training. This leads us to one of the first major things the movie says regarding the nature of a human being, or more, the nature of a sensitive simpleton when pushed by stereotypical trials of manhood. Pyle's attitude turns rather quickly when faced with extreme physical exertion and alienation by his brothers in arms. He has more than a failure to cope and develops a severe mental decline. The physical and mental abuse create a strain that Pyle is unable to cope with in a healthy way. So instead, he has a complete mental breakdown. The audience is shown one of the truths of humanity purported by the film. Ignorance, or an incomprehension of the strife and brutality that the wide world has to offer can change you. It can crush you if you are unwilling or unable to "man up". Pyle failed to fully embrace or conquer his physical training and peer strife. It was his failure to cope that lead to his breakdown.
Joker, on the other hand, follows the archetype of the hapless every-man with a sense of humor, that has to surmount those same difficulties. While the issues Joker faced with his peers are a poor comparison to those that Pyle faced, it can be argued that this is telling. Joker, was fortunate enough not to crumble under the initial pressures of their situation. Both, make targets of themselves when being lectured by their drill sergeant, but Joker is also able to deal with the embarrassment placed on him by his fellow soldiers by using humor, as opposed to simply taking it with a shrug and grin.