It's National Yo-Yo Day! Forget about all this satanic stuff, June 6th every year is National Yo-Yo Day (in the US) when children of all ages pull out their yo-yos and find internal happiness in the state of yo. The yearly day of recognition celebrates the birthday of of Donald F. Duncan Sr, the man who made the yo-yo popular in the US (You do know your yo-yo history don't you?). Of course, that isn't all that Duncan did in his life. He also founded the Good Humor ice cream company, invented the parking meter and made the concept of the premium incentive a popular marketing tool on top of founding the Duncan Yo-Yo Company.