As the year transitions from 1998 to a nostalgic past, identical twins David and Jennifer find themselves exploring a world that is both enchanting and bizarre while their mother is away. Their typical peaceful environment takes a turn when a dispute over the television results in a broken remote. When a TV repairman arrives, intrigued by David's love for Pleasantville, an old black-and-white sitcom featuring the idyllic Parker family, he gifts the boy an unusual remote control after being impressed by his enthusiasm. Curious about its capabilities, the twins start experimenting with it, only to be unexpectedly whisked away into the world of Pleasantville, where they are mistaken for the Parkers' children, Bud and Mary Sue.
Confused by the idyllic yet surreal situation, David attempts to engage with the repairman through the television, only to find that his pleas for help are met with indifference. The repairman believes they should appreciate the simple pleasures embodied by Pleasantville, a town where the impossible concept of fire doesn’t exist, and firefighters primarily rescue cats from trees, leaving the townspeople blissfully ignorant of the world beyond their borders.
As David urges Jennifer to conform to their new environment, she rebels, choosing to pursue a scandalous romance with Skip Martin, the school's most popular student. This bold choice triggers a colorful transformation, as vibrant hues begin to seep into the town. Bill Johnson, the owner of the local malt shop where Bud works, faces a personal crisis as he confronts the dull routine of his life.
David takes it upon himself to guide Bill toward breaking free from his monotony, all while sensing an attraction between him and Betty, his mother in the show. Meanwhile, Jennifer introduces exciting new experiences to her peers, like rain, which begins to redefine life in Pleasantville. With this shift towards open-mindedness, previously blank books in the library begin to fill with words as David and Jennifer narrate the plot of their favorite show.
Jennifer's influence also reaches Betty, who eagerly absorbs Jennifer's explanation about sex, setting her on a path to discovery and personal awakening. This newfound knowledge leads to dramatic changes, including Betty's transformation into color and the sudden ignition of a tree outside, symbolizing the town's encroaching evolution. As rain and new perspectives become commonplace, David shows Bill some modern art, compelling him to embrace painting and pursue a romance with the newly colorful Betty.
As Jennifer grows disenchanted with the shallowness of sexual escapades and parties, she finds refuge in books, which also contributes to her transformation. Strangely, David feels trapped in a grayscale existence, despite his romantic endeavors. The climax builds when Betty decides to leave George for Bill, shaking Pleasantville's conservative roots and causing Big Bob, the mayor, and other townspeople to question their cherished way of life.
Tensions ultimately erupt when Bill’s provocative artwork featuring Betty is displayed at his shop, inciting riots and chaos as “colored” citizens face harassment. Amidst this turmoil, David bravely stands up for Betty against a gang of unruly teens, marking his own vibrant transformation. In reaction to the perceived threat, town officials impose harsh restrictions, barring "colored" citizens from participating in communal activities, and even shutting down Lover's Lane while outlawing literature and rock music.
In defiance, David and Bill paint a colorful mural on their soda fountain, symbolizing love and artistic freedom. Unfortunately, their bold stand results in their arrest and a trial that draws the entire town's attention. During the trial, David confronts George about his lingering feelings for Betty, pushing him to recognize the depth of his emotions, leading George to undergo his own transformation.
As the townspeople embrace their changes, Big Bob remains resistant until he retreats in shame, facing the overpowering wave of evolution. In the end, the streets of Pleasantville, once confined, now lead to endless possibilities, and its residents celebrate their newfound freedom with color TVs broadcasting diverse programs from the outside world.
Jennifer decides to stay in the colorful realm of the TV world, bidding goodbye to her friends Margaret and Betty, while David returns to reality, where only a brief hour has passed. He comforts his mother, who had been anxious about a date. David's gentle reminder that life doesn’t need to be perfect resonates deeply, highlighting the significance of their adventures. In Pleasantville, however, the townsfolk embrace their vibrant reality, while Jennifer embarks on her next adventure in college, fully immersed in the beauty of her colorful surroundings.
