A boy is born without a body, only a head. For his 18th birthday his father, takes him to a bar for a drink.
The father orders his son a scotch and when the boy drinks it, an arm pops out of his head. He drinks another shot and another arm pops out. After the next shot a torso pops out. After more shots, suddenly, he has a whole body.
The boy runs out of the bar and gets hit by a truck, killing him instantly. A drunkard in the corner looks at the father and says, "He should have quit while he was a head."