The "Pen 15 Club" is an idea made up probably by immature young boys.
How It WorksEdit
Guy 1: Hey, dude, wanna join the Pen 15 club?
Guy 2: Sure, man. What do I do?
Guy 1: All you have to do is write "PEN15 CLUB" on your arm in permanent ink.
Guy 2 writes it on his arm
Guy 2: There, I did it.
Guy 1: HAHAHA YOUR ARM SAYS PENIS CLUB!!! YOU'RE SO STUPID!!!
See how it works? Now go and show your friends.