As the Walker family navigates the intricate challenges of their fractured lives in Los Angeles, the emotional rift between parents Jess and Bill, and their three children, CC, Wyatt, and Miles, is unmistakable. The well-meaning attempts by the couple to bridge the gap between themselves and their offspring often fall short, highlighting how each generation seems to communicate on entirely different wavelengths. As Christmas draws near, the family is thrown into disarray, with the parents aiming for unity while the children lean toward their own aspirations.
The tension escalates during a family trip to the Griffith Observatory, where they gather to witness a rare cosmic event. However, their outing takes an unexpected and chaotic turn when a dazzling flash strikes the observatory, leading to a profound sense of disorientation and detachment from one another. In the ensuing chaos, they unintentionally damage the telescope, sparking a series of unforeseen events that will impact their lives forever.
When the family wakes up the next morning, they are shocked to find themselves inexplicably linked by a mystical force: Jess and CC have exchanged bodies, as have Bill and Wyatt. The realization dawns on them that they must navigate their new and bewildering realities together. Seeking solutions, they reluctantly enlist the help of their unsuspecting neighbor Rolf to assist with toddler Miles and the family dog Pickles, who have also been implicated in this strange occurrence.
As the Walkers strive to cope with their new situations, their experiences in each other's bodies lead to disastrous outcomes. For instance, "Jess" (now CC) faces a nightmare while trying to deliver a vital presentation, only to be overwhelmed by a bout of lactose intolerance after indulging in ice cream. Meanwhile, "CC" (in Jess's body) accidentally sabotages her daughter’s soccer match to assist an injured rival, catching the eye of a national recruiter present at the game. In another chaotic twist, "Wyatt" (as Bill) manages to flub his son's Yale scholarship interview, squandering opportunities on both sides.
As they confront the aftermath of their body switch, the Walkers must also address the core issues behind their dysfunction and seek a way to revert to their own bodies before the celestial alignment passes. Tensions rise when they discover that the crucial lens for the telescope is missing, which is needed for it to operate properly. With the next celestial event looming a daunting 2162 days away, "Bill" capitalizes on an old favor to secure the component ahead of time.
In a moment of reflection, he confides in "Wyatt", who reluctantly agrees to accompany "CC" to a high-society gathering. Amid champagne toasts and canapés, "Wyatt"'s romantic intentions with Ariana falter, but he redeems himself by standing up to a bully terrorizing his son. Meanwhile, "Jess" and "Bill" steal away from the festivities for an intimate moment, only to be interrupted when "Bill" learns about "Wyatt"'s failed attempt with Ariana.
The next day, revelations unfold as each family member gains insights into the sacrifices their loved ones have made for their dreams. "Jess" learns of her mother’s relentless support for her soccer ambitions, and "CC" realizes the hard work her daughter has put into her studies. "Bill" discovers that his father sacrificed a flourishing music career to wholeheartedly embrace parenthood. Faced with the possibility that their individual dreams might have been lost in the cosmic mix-up, the family resolves to stick together through thick and thin.
United in their decision, they take to the stage during "Bill"'s music concert, collaborating with Jess's professional connections. Their performance becomes a triumphant success and secures Jess a promotion she deserves. Finally, with the telescope lens in hand, they rush to the observatory, aided by Angelica's timely intervention. However, their excitement is dampened when "Bill"'s hasty actions lead to the lens's accidental destruction. In a lucky twist, "Miles" had cleverly stashed the original lens before the switch, and they attempt to use it, hoping to achieve the elusive celestial alignment.
The following morning, an unexpected phenomenon occurs as the family finds themselves back in their original bodies. In a heartwarming moment, Wyatt and Ariana share a sweet first kiss, while CC is offered a second chance at national soccer tryouts by the recruiter who noted her sportsmanship during her previous game. Finally, Angelica bids the reunited family a warm Merry Christmas, driving away into the sunset, leaving behind a path of joy and rekindled connections.
