From Wikipedia:
Marvin Potts, an art director for a New York advertising agency, was hired by General Foods to create an image that would accompany the slogan "A 5-cent package makes two quarts." Inspired by watching his young son draw smiley faces on a frosted window, Potts created the Pitcher Man, a glass pitcher with a wide smile emblazoned on its side and filled with Kool-Aid.
The Kool-Aid Man was born in 1974.
But then there is an another article:
Kool-Aid, the popular powdered drink mix, was developed by Edwin Perkins (1889-1961) in Hastings, Nebraska. As a boy working in his family's general store in Hendley, Perkins became interested in a new powdered dessert mix named Jell-O and persuaded his father to carry it in the store.
