Conversation in the car...

Zane:  Mommy, where's Nigel's butthole?

Me:  Right under his tail.

Zane:  Where are his butt cheeks?

Me:  He doesn't have butt cheeks.  Just a hole.

Zane:  Why?

Me:  (sigh)  I don't know.  Maybe because he doesn't walk on two legs.

Zane:  Where's Cookie's butthole?

Me:  Under her tail, just like Nigel.  You just can't see it because of all her fur.

(thinking-pause)

Zane:  Cookie's a girl.  Does she have a pa-china?

Me:  Uhhh...I...don't...really know.

Zane:  Well, she's a girl, so she must have a pa-china.

Me:  Yes, well, she has something LIKE a vagina, but I don't know if it's called that.  I don't know what it's called.  Do you want to play with my phone?

Note:  Apparently female dogs have vaginas.  And that's what it's called.  And we will never speak of this again.