J Capp
When someone says this, it means you're about to get a real slap, or J-Capp is about to drop a rap so bad it'll make you cry.
'You called my mom J Capp? I'm gonna slap you until you're dead!'
'J Capp just started rapping. I'm gonna cry before the second verse.'
'He said I was J Capp. I hit him so hard the wall cried.'