This might be terrible parenting, but I am always thrilled when Simon discovers something he thinks will be a naughty activity but really isn't. It gives him the opportunity to be a little ornery, thinking I will soon chase him and wag my finger, but in reality I don't give a shit.
For example, today he found a roll of contact paper that I was planning to throw away in the near future. He had a bang up time unrolling it and running around the apartment dragging it behind him. Poor kid was trying so hard to be bad, but actually it was just good clean fun.