By day, Greg wants to build a very awesome model rocket ship, but all the supplies to build one is gone. Connor cheers Greg up about the trip to the science museum, but the teacher said that the trip was cancelled because there's no electricity. By night, it is revealed that Romeo wants to take over the town with his latest invention: The Big Box Of Bad! Robot says that Romeo is going to rename the town "Romeoville" or "Romeopolis (pronounced: row-me-aw-po-lis)" once Romeo's Big Box Of Bad is complete. Gekko gets mad, but then he finds out that Romeo booby-trapped all the tiles of the museum floor. Gekko's first trick is for Romeo to buy some Ice Cream, but then Gekko steps on another booby-trapped tile that spits out a gigantic boulder. Gekko gets steamed when the boulder crashes into his Gekko-Mobile, but then Catboy thinks of something: Stinky Cheese. When Romeo finds out about the Stinky Cheese, he stinks up the PJ Masks with "super super stink". But then, Romeo's Big Box Of Bad is finally complete, and "Romeopolis" is BORN!