Munro (1961)

Munro is a disobedient 4-year-old boy, who lives a normal life. Until he receives a notice that he is drafted. He fails to convince anyone in the army that he is only a boy, and eventually settles into the routine of army life. However when he is introduced as an experienced soldier to a group of new recruits, he begins to cry loudly. This attracts the attention of a general, who asks whether he is a soldier or a little boy. The general then realizes that Munro is actually a little boy, drafted by mistake. The general's subordinates also realize this. Munro is granted a military discharge, and receives a hero's welcome back home. But he lives in fear of returning to the army.