A young runaway finds himself in a diner, where he orders Pop-Tarts and becomes intrigued by the story behind the popular snack after reading the information on the Kellogg's box. Seated nearby is Bob Cabana, who offers to recount the real origin of this beloved breakfast treat.
The tale unfolds in 1963, with Bob as the head of development at Kellogg's in Battle Creek, Michigan. During this time, breakfast in America is largely dominated by milk and cereal, with Kellogg's and Post being the two major players in the industry. Leading Kellogg's is Edsel Kellogg, who regularly reviews sales figures with Bob. They soon find out that despite launching Fruit Loops, consumer feedback has been exceptionally poor. Bob, ever the innovator, suggests significant modifications to turn things around—doubling the sugar, tripling the gluten, and creatively spelling FRUIT as FROOT.
With Kellogg's coming out on top at the annual Bowl and Spoon Awards, Bob senses the looming threat of a new Post product, spearheaded by Marjorie Post and her assistant Rick Ludwin. Bob's instincts prove true when he sees children scavenging for discarded treats outside Post's headquarters, uncovering that they are developing a fruit-based pastry with an addictive quality.
As Bob investigates further, he learns that Post's new creation heavily borrows from concepts developed by his former colleague, Donna "Stan" Stankowski, which could threaten Kellogg's position. To tackle this issue, Bob persuades Kellogg to bring Stan back from NASA, and together with a quirky group of "taste pilots," including the likes of Tom Carvel, Chef Boy Ardee, and others, they embark on creating their own competing pastry.
However, tensions rise as Edsel warns Bob about stepping on the toes of the milk industry, a powerful faction led by Harry Friendly. The dairy moguls take drastic measures, including the abduction of Bob, which leads to a comical moment as he is forced to walk through a cow shed trail.
Simultaneously, Marjorie seeks sugar supplies in the USSR, worrying American authorities, including President John F. Kennedy, about the implications of a communist breakfast. Amid these conflicts, the taste-testing for their new pastry hits a snag when one of the taste pilots faces a tragic accident, yet their recipe remains viable.
In a twist, Thurl Ravenscroft, who plays the iconic Tony the Tiger, pursues a strike among the mascots, fearing that the new pastry will jeopardize his cereal mascot’s identity. The introduction of the cereal causes ripples through the industry, intertwining with historical events like the Cuban Missile Crisis.
Nonetheless, marketing struggles ensue as they attempt to name the pastry. Eventually, a major blunder leads the accidental renaming of their product to "Pop-Tart," sparking a frenzy upon launch, while rival Post's product flops.
The aftermath sees Lou facing consequences for the mascot-led protest, while the milk industry gets implicated in larger historical narratives. The story circles back to the runaway in the diner, where he questions the wild tale, and Bob reluctantly admits to embellishments. The surprising end sees the emergence of the elusive ravioli creature from his pocket, leaving the boy with a sense of wonder.
