An awesome one from reddit:
A perfectly normal couple has a baby, but, very unexpectedly, the baby is born without arms. Or legs. Or even a body. It's just a head...
Nevertheless, the couple embrace their roles as parents and, as unusual as it is, they raise their baby, trying to make his life as normal as possible. Obviously, it's a struggle, but they manage... and they love and treat their son like any other normal kid. Well, as much as possible.
On the day of their son's 21st birthday, the father decides to take his son for his first official real drink as an adult. So they go to the local pub, where the father proudly puts the head on the bar and orders two shots of the finest. The bartender can't believe what he's seeing, but goes and gets the drinks.
The father takes the drinks, cheers the glasses together, and takes down his shot while pouring it into his son's mouth. Lo and behold, the head starts wiggling and shaking and suddenly, dramatically, it sprouts an entire torso!!
"What the hell!?", screams the dad... "Bartender!! Two more shots!!"
And they do it again, and the torso and head start wiggling and shaking and BOOM, the son sprouts two arms!!
"Unbelievable!!", screams the dad... "Two more shots!!!"
And this time, of course, the son, delirious with happiness, does his own shot... and the subsequent shaking and wiggling leads to him instantly sprouting two legs!!
"Two more shots!!", screams the dad!!
"Holy shit!! Wait!!", screams the son, "Look! I can walk!! I can run!!" -- and with that, the son goes running out the door, straight into traffic, and gets obliterated by a bus.
"Hmmm... ", says the bartender... "Should've quit while he was a head."