The movie opens with a captivating sequence reminiscent of David Attenborough's documentaries, introducing the beloved characters in a charming manner. As the story unfolds, Gary the snail wakes up SpongeBob who excitedly teams up with Patrick to yell a cheerful good morning from their windows, unintentionally disturbing Squidward. Nostalgia washes over SpongeBob as he reminisces about the incredible moments shared with his friends before darting off to work.
Upon arriving at the Krusty Krab, he finds Squidward attempting to avoid him, only to be burned by the grill in the process. Mr. Krabs promptly puts SpongeBob to work, and the enticing aroma of the grill attracts a crowd of hungry customers. Plankton, on the other hand, is secretly spying through a telescope, plotting scheme number 3,087. His computer wife Karen reminds him of his past failures while suggesting that SpongeBob might be the real issue. Yet, Plankton remains convinced that Mr. Krabs is to blame.
In a surprising turn of events, Sandy bursts into the scene alongside a robot named Otto, whom Mr. Krabs hastily hires. However, the tables quickly turn as Otto fires Mr. Krabs and finds himself discarded into Plankton's trash, prompting Karen to intervene. As the day's chaos unfolds, Plankton, frustrated by his failures, attempts to steal the secret formula only to end up in a comical mishap involving a potato slicer and hot grease.
Meanwhile, in Atlantic City, King Poseidon admires his reflection but soon becomes agitated by a wrinkle in his skin. His Chancellor informs him of a shortage of snails, leading to a royal decree recommending the capture of a new snail. This unfortunate turn of events leads Plankton to decide that capturing Gary is the key to getting rid of SpongeBob.
Returning home, SpongeBob is distraught to find Gary missing and reflects on the fond memories from Camp Koral when he first met him. Shortly thereafter, Patrick enters and reveals the royal decree, prompting SpongeBob to feel overwhelmed with fear about retrieving Gary. However, Patrick offers to join him on an adventurous road trip, accompanied by Otto. Their journey, though filled with miscommunication, brings them closer. Yet, their bond is tested when they argue and inadvertently crash into a billboard, only to reconcile and continue their quest.
Back at the Krusty Krab, the situation escalates as customers grow impatient and Squidward mishandles the grill, leading to chaotic consequences. SpongeBob and Patrick find themselves on land where they initially question their reality, before entering Goner Gulch, where they encounter Sage, a tumbleweed character who gifts them a "courage coin." Ignoring Sage's guidance, the duo rushes into a saloon filled with dancing zombie cowboys, where a fantastic performance led by Snoop Dogg unfolds. However, they soon find themselves trapped by El Diablo. In a climactic moment, SpongeBob and Patrick open the curtains, incinerating El Diablo and freeing the zombies, which allows them to escape.
Sage then reveals a troubling truth about Gary's potential suffering, pushing SpongeBob and Patrick further into action. As they navigate trouble back at the Krusty Krab, the stakes heighten with SpongeBob and Patrick confronting Poseidon in Atlantic City, where they meet challenges and tests of friendship at every turn.
With the situation worsening and the execution approaching, Patrick reminds SpongeBob of their mission and the courage they possess. They cleverly devise a plan to reveal the truth to the audience, culminating in a heartfelt musical number led by Mr. Krabs. Together, the friends, through hilarious antics and clever strategies, manage to regain control of the situation, leading to a poignant reunion with Gary.
In a surprising twist, King Poseidon realizes the value of friendship as SpongeBob reaches out with compassion, much like how he befriended Patrick. This revelation transforms Poseidon, allowing SpongeBob to keep Gary, as all the other snails are freed too.
The movie concludes with a whimsical return to Bikini Bottom, where the once-pet-less town is now bustling with happy snails, symbolizing friendship, unity, and joy.
