Smart Aleck
One sergeant gave an order for the whole company to raise the right leg. One confused draftee raised his left leg in error. The sergeant looked down the line and saw the upraised left leg of one soldier right next to the upraised right leg of the recruit beside him.
"Who is that smart aleck* in the middle of the line," he bellowed, "who raised both legs?"
*A smart aleck, also spelled smart alec, is someone whose sarcastic, wisecracking, or humorous manner is delivered in an offensive, obnoxious, or cocky way.