In the year 1962, brothers "Buffalo" Bob and Horatio P. Huntington effectively ran a traveling circus, thriving despite their starkly contrasting personalities. After one entertaining show, the circus's enchanting gypsy fortune-teller, Esmerelda, introduces her stunning niece, Talia, to her equally captivated employers. Although both brothers find themselves fascinated by her beauty, Talia's heart only belongs to Bob.
When Bob and Talia announce their engagement in 1964, Horatio's fury boils over, insisting Bob must choose between him and Talia. Bob ultimately marries Talia, and as a wedding present, Esmerelda gifts them a mysterious box, which becomes instrumental in the establishment of their new venture: Buffalo Bob's Rootin' Tootin' Animal Circus, renowned for showcasing animals performing jaw-dropping feats.
Fast forward to years later, where Bob's nephew Owen ties the knot with his childhood friend Zoe at the very circus where their paths first crossed. However, the thrill of the wedding quickly dwindles as Owen's new reality dawns: he is drafted into the role of taste tester at Zoe's father's dog biscuit factory. There, he must contend with his eccentric co-worker Binkley, who is desperately trying to invent a revolutionary dog biscuit, only to have his efforts sabotaged by Mr. Woodley's questionable assistant, Brock.
After some time, Horatio experiences a drastic downturn in fortune. In a desperate attempt to discover the secret behind the magical animals, he intrudes upon Bob and Talia's dressing rooms, inadvertently starting a fire that appears to take the lives of the couple. The tragedy profoundly impacts Owen, Zoe, and their daughter Mackenzie, who gather at the couple's funeral. To everyone's shock, Horatio arrives unannounced, proclaiming his intent to take control of the circus. But when Horatio and his minions—Mario Zucchini, Samson, Stabby, and El Diablo—initiate a brawl, the Huntingtons are forced to flee.
Before leaving, the beloved circus pets, Old Blue and Zena, gift the mysterious box to the Huntingtons, who soon uncover its magical contents: animal crackers. In a moment of curiosity, Owen samples one and hilariously turns into a hamster. Determined to get to the bottom of this enchantment, the Huntingtons return to the circus, learning from the clown, Chesterfield, that these animal crackers can transform anyone into the animal they consume. However, there's only one human cracker in the mix to revert back to human form. Zoe is eager to take on the circus's legacy, but Owen feels obligated to fulfill his duties at the factory.
As the newly revived circus kicks off, catastrophe strikes when they realize they have no animals left. Owen reluctantly decides to indulge in the animal crackers, performing amazing stunts as various animals. Gradually, he begins to enjoy this unique talent, but just as he is set to abandon his factory job, Brock mistakenly eats an animal cracker and transforms into a mandrill. To rescue him, Owen assumes the form of a lion, but things go awry when Mario Zucchini captures Brock and absconds with some animal cracker pieces.
Realizing he has lost the crucial human cracker, Owen faces the daunting task of navigating life as an animal. Although he tries to adjust, he encounters constant challenges. Meanwhile, Binkley instinctively pushes Mr. Woodley to attend the circus, hoping to turn things around. During one memorable performance, Horatio presents Owen, now in a mountain gorilla form, with his human cracker as a bargaining chip for control over the circus—a deal Owen staunchly declines, believing that staying an animal will maintain family unity.
When Horatio initiates a backup plan to force Owen into submission, chaos ensues as the circus performers intervene, some shapeshifting into animals. In the ensuing mayhem, Horatio consumes animal crackers, transforming into a fearsome six-limbed Chimera. Just then, Old Blue and Zena reveal their true identities as Bob and Talia, who have remained alive but trapped in animal forms due to the fire that destroyed their human crackers. They plead for Horatio's redemption, which he coldly refuses despite his horror at the consequences of his actions.
In a heroic moment, Owen, using Bullet Man in his black rhinoceros form, takes a bold stand against Horatio as he, along with the rest of the circus, band together to thwart the villain's plans. Ultimately, after an epic confrontation, Owen manages to turn Horatio into a hamster, delivering a profound quote from Alfred Lord Tennyson, “In Memoriam A.H.H.”
As order is restored and the circus performers, Owen, Zoe, and Mackenzie regain their human forms, Chesterfield cheerfully informs the captured henchmen that their human crackers are broken, leaving them ensnared in a comical predicament. Meanwhile, Mr. Woodley reevaluates his stance on Owen and the circus after witnessing the performance, leading him and Binkley to create a new circus souvenir inspired by her previously thwarted endeavors.
In a twist of fate at the upcoming show, they unveil a new kind of animal cracker that temporarily alters the consumer's appearance to match the colors and patterns of the animal cracker they choose. With excitement brimming, Owen consumes a fresh animal cracker from the box and takes center stage as a dazzling dragon, ready to unleash a world of wonder.
