After finding out the map they were given at the end of their last adventure will lead them to the Dragon Lands, the Mane 6 head there to let the dragons know that Opaline isn't a danger to them anymore. But while they are convincing the dragons they mean no harm, they are called on another Unity Quest... this time, it may be their biggest adventure yet.

When SpongeBob’s beloved pet snail Gary is snail-napped, a trail of clues lead him, Patrick, their sea-unicorn companions and the Mane 6 to the powerful King Poseidon, who is keeping Gary in the Lost City of Atlantic City. 

But… he’s not the only villain in this story that our heroes will have to deal with. Allura and her minion Twitch are here as well, looking for a fragment of a very powerful star that will lead Allura to other realms, and Sunny and her friends already have one of those pieces in their possession already. If she gets the rest of those pieces and combines them, she will be unstoppable.

On the mission to save Gary (and unknowingly, the entire ocean from Allura), the Mane 6 team up with Bikini Bottom friends, old and new, on a hilarious and heartwarming journey where they discover nothing is more powerful than family and true friendship.

(S3E3 of G5 Adventures)