As Molly attempts to introduce the show, Gil presents her with several items that a princess would wear: a necklace, fancy silk gloves and a shiny crown. At that moment, a unicorn appears from behind a throne and whinnies loudly, scaring Gil away! The 'unicorn', however, turns out to be Oona in a costume, and she proceeds to introduce the show by announcing: "It's time for Bubble Guppies!"
On their way to school, Molly and Gil come across Demanda, a princess-in-training, who is practicing her throwing skills. Although talented physically, she appears to be quite bad mannered and acts rude towards her mother, the Queen. Molly finds out that in order for Demanda to become a true princess, she must complete the 'Glitter Games', a challenge in which young girls must prove that they have the qualities of a proper princess, which include good manners. Molly reveals that she wants to be princess too, and the queen encourages her to compete in the games, as anyone who completes the challenge will become one. Demanda continues to act rude as Molly and Gil say goodbye and head to school.
When they arrive, Molly and Gil tell everyone about Demanda, the soon-to-be princess. Soon, Mr. Grouper gets everyone talking about princesses, including what they wear and how they are supposed to have very good manners, as should everyone, whether they are royalty or not.
This inspires the Bubble Guppies to sing So You Want To Be A Princess!
After the song, Deema invite the viewers, and Nonny, to play 'The Princess Is Right!', a game show all about good manners. In order for the princess to save the knight, Nonny must correctly answer questions on how to use good manners. With the viewer's help, Nonny answers that it is right to say 'Please' rather than 'Gimme!', and 'Thank you' when someone gives you something. Nonny also gets bonus points for saying 'You're Welcome' when Deema thanks him. Mr. Grouper then announces politely that it's time for lunch.
Molly tells the viewers that princesses like to dress up in fancy clothes, when Gil wanders past her with a camera. He is determined to get a photo of the 'unicorn' that startled him earlier, despite Molly telling him that unicorns don't really exist. Gil follows some suspicious tracks and walks backwards - right into a unicorn horn! This time the unicorn is Bubble Puppy, who playfully chases after Gil as he rushes away. Oona and Molly invite the viewers into the classroom, where everyone is playing princesses. Mr. Grouper pretends to be a dragon, scaring everybody but Molly, who reprimands him on his bad manners. It's then time to go outside.
In ancient Mexico, Knight Gil and Princess Oona are having a picnic. Both are very polite with their manners. However, their polite picnic is soon rudely interrupted by 'Pretzelquatl', an ancient serpent monster who loves pretzels. Oona and Gil rush to a quieter spot by a river, but, once again, they are interrupted by the bad mannered serpent. They run away again, and decide to hide in a nearby pyramid, but Pretzelquatl finds them once more. Oona has had enough, and tells him that he is behaving impolitely, asking the viewers to help him with his manners. Instead of just saying 'Yummy!' to get attention, Pretzelquatl asks politely for a pretzel, making sure to say 'Please'. Oona, Gil and Pretzelquatl share the picnic and live politely ever after! Molly then invites everyone to do The Princess Dance!
After the dance, Gil is still intent on getting a picture of the unicorn, attempting to use good manners this time. Gil politely asks the unicorn to come out from behind a bush but, once again, it's Oona, who gives him another fright and gallops away before Gil can take a photo. Mr. Grouper then informs everyone that it's time to go to the Glitter Games!
At the games, Molly joins Demanda and two other contestants at the start line, while her friends cheer from the stands. Demanda is adamant that she will win, and rebuffs Molly's polite gesture of wishing her good luck. To the charming tune of the bard, the games begin. Demanda leads the way in all of the physical challenges. Molly keeps a close second whilst the remaining contestants fail to reach the door of the castle. To pass through the doors, Molly and Demanda must show their good manners. Molly passes the test fine, but Demanda struggles to remember what to say when someone gives you something. With the viewer's help, Demanda correctly answers 'Thank You'. Demanda apologizes to her mother for being rude before, and both girls pass through the gates and become princesses!
Just before the show ends, Gil congratulates Molly and Demanda on becoming princesses. Gil asks them to help him find the unicorn, and as luck would have it, Demanda has the unicorn's number on her phone. Gil asks politely to speak to the unicorn, who is actually closer than he thinks! This time, both Oona and Goby are masquerading as the unicorn and give Gil one last surprise. Everyone laughs as the show ends.