CIRCUMCISED skin, doesnt, second

zhoujiazui741

Two five-year-old boys are standing at the potty to pee.  
One says, "Your thing doesnt have any skin on it!"  
"Well, Ive been circumcised," answered the other one.  
"Huh, Whats that mean?" asked the first boy.  
"It means they cut the skin off the end," said #2.  
The first boy was very puzzled, "How old were you when  
it was cut off?"  
本o文0摘t自＆j^p^z^y^z点c^o^m

The second boy replied, "My Mom said I was only two  
days old."  
"Wow, did it hurt?" the first boy wondered.  
The second boy responded without hesitation,  
"You bet it hurt...  
...I couldnt walk for a year!"

lingkiki

fun

呆了

I can't understand it. Why is it funny?