What is it About the ...?

So we have all seen this picture before. Joseph in his cute khaki hat with a dandelion in hand. Today, like most days in the Spring and Summer, Joseph and David play outside, and intermittently I come outside to visit and take pictures.
But then something distracts Joe from our impromptu photo session. It's something a lot of little boys find fascinating. David says, little boys love these because they are big and loud. I think it's because they are stinky...

The trash truck.

Ooooo, awwww, mesmerizing!