Before having our youngest son we already had a boy and a girl so thought we were ready for anything and had all of the baby clothes, equipment, toys and so on. That was true until he was about 18 months old.
Like most parents we went around the house and double checked our baby proofing. All was well until he figured out how to use prying tools. With these instruments of potential death he would work on the plastic electrical plug protectors out of the wall. Repeated attempts to discourage this behavior did not seem to diminish his enthusiasm. In fact it increased when he got tired of using plastic objects and moved on to their stiffer more efficient metal cousins. This forced us to get a more sophisticated plug protector which took a significant amount of adult effort and dexterity to open. Even with those credentials he still attempted to open the plug covers but was never successful.
Flash forward 13 years and he was helping me in the yard a few months ago. In my effort to reduce-reuse-recycle, I had taken one of these covers and placed it over the end of a modified extension cord. This allows the cord to be used outside, protected from the elements and any neighborhood little ones cannot get into it during our Halloween and Christmas lighting displays.
At 15 he is now over 6 feet tall and over 200 lbs, yet just as when he was less than 2, the plug cover thwarted his attempts to open it. After showing him how it worked I told him the story of why we obtained that cover in the first place and he had a good laugh about it.