"The head" joke

A man is waiting for his wife to give birth. The doctor comes in and informs the dad that his son was born without a torso, arms or legs.
The son is just a head!
But the dad loves his son and raises him as well as he can, with love and compassion.
After 21 years, the son is now old enough for his first drink. Dad takes him to the bar, tearfully tells the son he is proud of him and orders up the biggest, strongest drink for his boy.
With the entire bar patrons looking on curiously and the bartender shaking his head in disbelief, the boy takes his first sip of alcohol.
Swoooop! A torso pops out! The bar is dead silent; then bursts into a whoop of joy.
The father, shocked, begs his son to drink again.
The patrons chant "Take another drink"!
The bartender still shakes his head in dismay.
Swoooop! Two arms pop out! The bar goes wild.
The father, crying and wailing, begs his son to drink again. The patrons chant "Take another drink"! The bartender ignores the whole affair.
By now the boy is getting tipsy, and with his new hands he reaches down, grabs his drink and guzzles the last of it.
Swoooop! Two legs pop out. The bar is in chaos.
The father falls to his knees, overcome with joy.
The boy stands up on his new legs and stumbles to the left, then to the right... Right through the front door, into the street, where a truck runs over him and kills him instantly.
The bar falls silent.
The father moans in grief.
The bartender sighs and says, "He should have quit while he was a head"