Assuming he survived childhood, the young daredevil shown here has been drawing Social Security for about six years now. He is shown attempting to poke his fingers into the outlet in the September 1944 issue of Popular Mechanics.  The accompanying article explains how to make the dummy plug shown in the inset.

Just in case mom and dad didn’t figure it out, the article points out that to use the outlet normally, “the dummy plug can be removed and a plug with wires inserted in its place.”