Little Billy sees his Grandpa smoking a cigar.

Billy asks, "hey Grandpa, can I get a puff of that cigar?"
Grandpa replies, "Well Billy, does your penis touch your asshole?"
Billy looks down and says "no, my penis does not touch my asshole."
"well, you can't have a puff of my cigar" says Grandpa.
Later, little Billy sees his Grandpa drinking a beer and asks "Hey Grandpa, can I have a sip of that beer?"
Grandpa once again replies, "Does your penis touch your asshole?"
Billy looks down and says "no my penis does not touch my asshole."
Later, Grandpa sees Billy eating some milk and cookies and asks. "Hey Billy, can I get some of your milk and cookies?"
Billy asks "Well Grandpa, does your penis touch your asshole"
Grandpa replies "Hell yes my penis touches my asshole!"
Billy says "Good, then you can go fuck yourself! These are my milk and cookies!"