3 guys walk into a bar ...
The first guy says "I've got the smallest arm in the world."
The second guy "Oh yeah, well I have the smallest head in the world."
The third guy "Well when it comes to small body parts, I have you both beat. I've got the smallest *
gender defining appendage* in the world."
So the 3 guys decide to settle their argument the only way they know how, and pay a visit to the good people at Guinness...(the world record people, not the brewers

)
The first guy comes back and says "I really do have the smallest arm in the world."
The second guy comes back and says "Amazing, I do have the smallest head in the world."
The third guy comes back angry "Who the HELL is JUSTIN BEIBER!?"