Is this an early Duplo mini figure?
At last, I have your answer. The figure is from a "Giant Pre-School Loc Bloc" set, likely the "Playground" one shown in the picture.  

Nearly a month later, while doing unrelated research, I found "Giant Brix Blox", a second possible source of these types of figures;  



It makes since given that sources claim Loc Blocs &amp; Brix Blox were both imported from the Japanese company Kawada.