When a passing truck covers Gump's face with mud, he cleans it off with a yellow T-shirt, leaving the salesman with a smiley face. The battle over the image took center stage in the late 1990s.

2. The first World Smile Day was held in 1999. Concerned that the smiley face had been overtaken by commercialization, Mr. Ball came up with the idea of an annual celebration of pure happiness.