boys and poop

I don't understand what it is that makes boys fascinated with anything gross.  Maybe it's just my boys?  I don't think so.  Cooper told a joke on our drive from Utah to Washington.  It's one he heard while watching "Wreck It Ralph." 

 It goes like this: 

"Why did the hero flush the toilet?... 

Because it was his DUTY!"  

And Brent LAUGHED.  

Hard.  

He loved it.  

So now Cooper says it all of the time.

Well, this afternoon when Lincoln needed some "assistance" in the bathroom, he told me that what he had deposited in the toilet was: 

"STAR WARS poop."  

Then he explained that he was playing STAR WARS and described everything going on in his imaginative little brain.  

Again, I ask:  "What is it with boys and gross-ness?"