Smiley
The design was made popular in the early 1970s by a pair of brothers, Murray and Bernard Spain, who though of a great plan to sell novelty items. The two used the "smiley face" on buttons as well to decorate coffee mugs, t-shirts, bumper stickers and many other things. They also used the phrase "Have a happy day" (which was the idea of Gyula Bogar). "Smiley" buttons were very popular from the 1970s onwards.