The Chief arrives in Pepperland with his army of Meanies and begins his campaign of taking over by firing a massive glass sphere at the Beatles' doubles, Sgt. Pepper's Lonely Hearts' Club Band, who play music all day in this colorful world, while all the natives dance and sing and generally behave in a friendly manner towards one another. As the Chief comments, "it can't last". The soundproof glass sphere covers the band, making their music inaudible, and in their panic to run away, the natives are fired at by the Blue Meanies' guns, whose missiles both drain their victims' colour on contact and petrify them.
The Chief bombards the natives with various weapons and species of Meanie that vary in their ferocity and eccentricy– anything from Meanies that will eat the toys of young children (as demonstrated when the Beatles' arrival to Pepperland, when a sharp-toothed Meanie, a snapping turtle-turk, consumes a young girl's paper windmill) to reducing the flourishing hills and plants to a land of bare thorns and colourless grass, with the only green existing in the form of giant apples that the "Apple Bonkers" (taller Meanies) drop on peoples' heads. Later in the film, the Chief engineers the kidnapping of the Beatles' friend and comrade, the Nowhere Man Jeremy Hilary Boob. When the Beatles finally arrive in Pepperland, the Chief is woken from a brief sleep and is incensed when he sees the hills and trees returning to their proper colours at the sound of their music; he sends his fiercest weapon, "The Dreadful Flying Glove" after the heroes. The Glove is thwarted by John Lennon's song "All You Need is Love" and the Chief's army flees, knocking him over in the process. In a final, petty attempt at retribution, the Chief threatens to tear the newly-freed Nowhere Man into "blue burgers".
However, he is humiliated by his magic and ends up sprouting flowers from his nose and body. He flees with the rest of his army, but later contemplates "mixing" with the Beatles – however, at the very end, when the Beatles appear in the flesh to the audience, Lennon says that "Blue Meanies have been found within the vicinity of this theatre".