A boy and his grandfather go fishing.

While they're out there, the grandfather pulls out a cigarette and starts smoking it.

The boy asks "hey grandpa, you think I can have one of those?"

"Well can you reach your asshole with the tip of your penis?" The boy responds with no.

"Then you ain't old enough for a cigarette."

Later on, the grandfather pulls out a beer from his ice chest.

Again the boy asks, "hey, do you think I can have a beer grandpa?"

And again the grandfather replies "Well can you reach your asshole with the tip of your penis?" The boy has no other answer then "no".

"Then you ain't old enough for a beer son"

More later on, the boy pulls out a Snickers.

The grandfather asks "hey boy, give me a piece of that snickers."

Thia time the boy asks "well grandpa, can you reach your asshole with the tip of your penis?"

"Son, you bet your ass I can"

"Well then you can go fuck yourself."