The Bubble Guppies learn all about different kinds of clothes, costumes and fastenings, and Molly performs in the big quick-change dress-up match!
Molly swims into view, ready to introduce the show, when Gil leaps out of a nearby wardrobe dressed as a rock star! After a few strums, he hops back inside the wardrobe. A little confused, Molly tries again to open the show, but not before Gil bursts out again, this time dressed as a football player! He hurls the ball and returns back inside the wardrobe. Molly tries one more time, but once again Gil leaps out of the wardrobe, this time dressed as a mouse! Molly sneaks inside the wardrobe whilst Gil is scurrying and squeaking. Just as Gil notices Molly is missing, she leaps out of the wardrobe dressed as a cat, scaring Gil away! Molly finally gets to say: "It's time for Bubble Guppies!"
Molly and Gil come across a big photo-shoot, where a stylish snail, dressed as a cowgirl, is posing for the camera. They meet Ms. Fancy Fuss, who is searching for the next best thing to appear on the front cover of 'Dress Up' Magazine, the hottest fashion magazine in Bubbletucky. Only something very special and original will be chosen for the front cover. In Ms. Fancy Fuss's words: It needs to have 'It'. Molly and Gil say goodbye and head to school.
Molly and Gil tell the rest of the Guppies about the costume photo-shoot, and all of the guppies love to dress up in costumes. Goby reveals that he dresses up in a uniform when he plays baseball, and Oona and Nonny talk about how dressing up can be difficult with all the zips and buttons involved. Mr. Grouper gets all the guppies talking about different costumes, which inspires them to sing Dress Up!
After the song, Goby pays a visit to Deema's 'Dress Up Warehouse' to find a costume for his action figure. Goby wants his toy to dress up like a pirate, and Deema provides everything - except for a decent pair of boots (pirates definitely don't wear ballet slippers). Deema and Goby turn to the viewer for help in choosing the right boots for his action figure. After choosing the right boots, Goby's action figure is finally all dressed up! Mr. Grouper then announces that its lunchtime.
Molly tells the viewers that dressing up can make you feel like someone else, as Gil wanders over to a costume box. He dresses up a police officer, but feels like he is missing something. At that moment, Oona (who was hiding in the costume box the whole time), jumps out and blows a police whistle, the item Gil was missing, scaring him away in the process! Deema then appears and invites everyone to come play dress up. In the classroom, Deema presents her own fashion runway, with Gil and Nonny as the audience members. Goby is first up, buzzing onto the stage dressed as a bee! Next up is Oona, dressed as a police officer. Molly is last, wearing a mash up of different clothes, which she calls a 'Molly Original'. It's then time to go outside.
Oona and Nonny are 'Dress up' police officers, whose job is to help people dress up in the right costumes. On their patrol, a dress up emergency call is received, and they rush to the scene - at the fire station. Molly is dressed up like a chef, which is not appropriate clothing for fighting a fire. With Oona and Nonny's help, she finds the right costume - a firefighter uniform. But before they can celebrate, a gorilla appears, scaring everyone away! With Molly in tow, Oona and Nonny get another emergency call, this time at the beach, where Deema is trying to hula dance in an astronaut uniform. With the Dress Up police's help, Deema can finally dance in a proper grass skirt. The gorilla appears again, and everyone rushes for the van! After escaping the gorilla, yet another emergency is received, this time at a football game, where Gil is dressed completely different from his team. With the viewer's help the Dress Up police select the correct uniform and Gil is looking great in no time! However, as it turns out, the gorilla is just a monkey dressed up in a costume, and couldn't get it off. They help the monkey remove the costume, and he chooses his next costume to be a police officer, just like Oona and Nonny! Deema then invites everyone to do the Zip Up! Zip Down! dance!
Gil is dressing up again, this time as a knight. He explains how knights are brave and fight dragons. At that moment, Nonny emerges from the costume box, dressed like a dragon, frightening Gil away! Mr. Grouper then takes everyone to the big costume boxing match!
We are joined by announcers Nonny and RuPearl as they commentate on the big dress up match. It's Mi-chelle the snail verses Molly and the crowd is on the edge of their seats! Mi-chelle manages to zip up her jacket faster than Molly, winning round one. In round two, Molly is the victor, managing to button up her shirt quicker than Mi-chelle, who misses a button. Round three demands that both contestants put on a jacket that has both buttons and a zipper! With the viewer's help, Molly finds the right jacket, and during a tense round of buttoning and zipping, both competitors stumble and fall. Molly emerges from the costume box victorious, wearing a mix a different clothes, which Ms. Fancy Fuss deems perfect for the cover of her magazine!
Just before the show ends, Gil congratulates Molly on her success while dressed like a banana. Suddenly, the monkey from earlier arrives, dressed as the gorilla again, making Gil the banana dash for safety! Everyone laughs and the show ends.