What's the difference between Oo and oO?

Two young guys appear in court after being arrested for smoking dope.

The judge says, "You seem like nice young men, and I'd like to give you a second chance instead of jail time. I want you to go out this weekend and try to convince others of the evils of drug use. I'll see you back in court Monday."

On Monday, the judge asks the first guy, "How did you do over the weekend?"

"Well, your honor, I persuaded 17 people to give up drugs forever."

"Seventeen people? That's wonderful. How did you do it? "

"I used a diagram, your honor. I drew two circles like this: O o. Then I told them that the big circle is your brain before drugs and the small circle is your brain after drugs."

"That's admirable," says the judge. Then he turns to the second guy. "And how did you do, son?"

"Well, your honor, I persuaded 156 people to give up drugs forever."

"Wow!" says the judge. "156 people! How did you manage to do that?"

"Well, I used a similar diagram," the guy says. I drew two circles like this: o O. Then I pointed to the little circle and said, "This is your asshole BEFORE prison...”