willpower vs. Will power

Yesterday morning, while I was in the house getting Will ready for church, Joe took Nathan out to get into the car.  Joe asked Nathan to get into his seat and instead Nathan went over to ride his scooter.  Joe told Nathan "Nathan, come to the car, you have the willpower!"  Nathan replied "I don't have Will power, I have Nathan power!" 
FYI Nathan, Daddoe wasn't talking about your little brother!  :)