Who pees on a dog?!

Our Beagle, Montana

My four year old boy has been potty trained for almost two years now with no major incidents - that is until a couple months ago...

I was sitting in our living room when I observed the family dog come running into the room and begin furiously rubbing his face and back on the rug.  "What on earth?" I thought.  As I knelt down to check him, I observed that his fur was wet.  Immediately, I went on the hunt for the cause of such wetness.  That's when I saw him, my son, standing half-naked in the bathroom.  "Josiah!  Do you know why the dog is wet?" I exclaimed.  He replied, quite matter-of-factly, "Yes, I peed on him."  Then he broke into a huge grin.  I immediately informed him of how mean that was and made him wash and dry the dog.  However, I couldn't help thinking the rest of the day. "WHO PEES ON A DOG?!"