I'm Starting To Get Concerned...

I needed to run to the store today and Bird was going to a PTO meeting.  Therefore, I was taking the boys with me.  We piled into the truck and as I'm backing out of the garage Sam (9) asks me if I'd like to hear a dirty joke.  "Sure," I say a little wary of what might be coming.  The joke went like this:

Mickey's car breaks down somewhere and he calls Minnie for help.

Mickey: Can I stay at your place tonight?
Minnie: Okay, but you have to sleep on the couch.
Mickey: Can I please sleep in your bedroom?
Minnie: Okay, but you have to sleep on the floor.

They start out in this arrangement, but very late into the night Mickey wakes up.

Mickey: Can I sleep in the bed?
Minnie: Why?
Mickey: Please?
Minnie: Okay.
Mickey: Can I poke your belly button?
Minne: Why?
Mickey: Please?
Minnie: Okay. Hey! That's not my belly button.
Mickey: It's okay. That's not my finger.

Sam with a silly grin on his face asks, "Get it? Do you know what he poked her with?"  I said, "I'm pretty sure, yeah.  But what do you think?"  Sam answered, "His thingy."  Still being a little wary I said, "Yes, and where did he poke her?"  His answer was, "Between her boobs."  I could only say, "Yeah, Sam that was a little dirty."

He just doesn't seem mature enough for the talk yet, but if this keeps up I'm going to have to set the record straight or else he'll have a serious uphill battle for the rest of his life.