Cake Decorator

To celebrate C's birthday last week, I got a store-bought cake.  My plan was to let DD decorate it which he did so happily.  I gave him a bowl of nonpareils and let him do what he wanted.  He stood on a stool for at least 10 minutes gingerly sprinkling little bits of nonpareils on the cake.  I thought he would sprinkle them all over the white frosting but he didn't.  He concentrated his sprinkling in the center.  Later, I figured out why.

When it was time to eat, he asked C to cut him the center piece, the one with the most nonpareils.

P.S. See that corner of the cake with the frosting missing?  Can you take a guess what happened there?