Pep became one of the first "fortified" cereals, with an infusion of vitamins, beginning in the 1930s. Extensive advertising, from print advertisements to sponsorship of The Adventures of Superman, helped keep the brand in the public's consciousness. Pep was included in "variety packs" of serving-sized boxes of Kellogg's cereals. The cereal's "mildly laxative" property was routinely mentioned in print ads. Despite its pluses, Pep faded from popularity as public tastes changed, and the brand was discontinued in the late 1970s.
In 1945, Kellogg inserted a prize in the form of pinback buttons into each box of Pep cereal. Pep pins have included U.S. Army squadrons as well as characters from newspaper comics. There were five series of comic characters and 18 different buttons in each set, with a total of 90 in the collection. Mint condition Pep pins, as with prizes from many cereal brands, have become sought-after collectables.