Ralston Purina's line of cereals have always been running far, far behind Kellogg's, General Mills, Quaker, and Post in terms of popularity. In fact, today, most of the surviving Ralston Purina cereals, including Chex, are made by General Mills.
In 1968, Ralston Purina introduced a trio of youngsters known as the Chexmates.
To be honest with you, gang, this is the first time I've seen this ad. I was in kindergarten when this originally came out, and had no memory of seeing this before.