"Grandpa and Grandson" joke

A grandpa and his five year-old son went out fishing. After a while the grandpa pulled out a beer and the grandson asked "Hey Grandpa, can I have a beer?"
The grandpa replied by saying "Can your dick touch your asshole?"
So the grandson said,"No."
Then the grandpa said, "Then you can't have one."
Later on, the grandpa pulls out a cigarette and lights it up and the grandson asked "Hey grandpa, can I have a cigarette?"
The grandpa again replied by saying, "Can your dick touch your asshole?"
So the grandson again replied by saying no.
Then the grandpa said, "Well, then you can't have one."
Now the kid is getting really pissed off. So he takes out a cookie and the grandpa says, "Gee grandson, can I have one?"
The grandson replied by saying, "Can your dick touch your asshole?"
So the grandpa said, "Yes."
Then the grandson said, "Good, then go f*** yourself because grandma made these for me."