Shenanigans abound after Rousso makes his special cookies for the boys down at the fire station. Later, Jonas and Wimzie accidentally drop the cookie tin. Scared that they may have broken the cookies into little pieces, they keep the cookie tin out of Rousso's sight. To do so, they have to hide, run around and lie about the tin's whereabouts. They end up getting deeper into trouble than if they'd told the truth. Later, Horace accidentally sends the tin crashing to the floor again, in front of everyone. He starts crying because he thinks he's broken the cookies. Seeing their friend cry, Jonas and Wimzie are quick to confess that if the cookies are broken, it's their fault. In the end, the situation is cleared up and, when Rousso opens the tin, he discovers that the cookies were so hard they didn't break at all.

Wimzie thinks it's great fun to play the "Boo!" game, which means sneaking up behind people and scaring the pants off them with a loud "Boo!" Jonas, however, wants to be left alone to play quietly with his dirt collection but is afraid to say so for fear that Wimzie won't like him anymore. With Yaya's help, he'll manage to express his feelings about how he'd rather play quietly by himself, even if that means being different from the others.

To help Horace get over his general grumpy mood, Yaya makes him a magic crayon that can draw in the air. Loulou finds it and, not knowing that it belongs to Horace, she gives it to Wimzie as a gift. Meanwhile, Jonas arrives with his "Mevoca", a special voice-disguising megaphone toy for his budding spies. Horace, who's seen Wimzie parading with his magic crayon, is very angry and just can't seem to tell her that he wants it back. With Yaya's help the matter is cleared up, showing that it's better to say what's bothering you than to keep it bottled up.

Wimzie is over the moon! Graziella has a day off and is going to spend it with her little girl. But Bo gets sick and Graziella's attention is turned to him. Wimzie is not pleased, starts acting out and pretends to get sick herself in order to get Graziella's attention. She ends up making her mom's day even more difficult. When the all-knowing Yaya, who suspects skullduggery, comes to administer some "delicious" mustard water to cure her mysterious and sudden illness, Wimzie is quick to confess and apologize to her mom. Graziella explains that sometimes, she may have to give a lot of attention to her brother but that doesn't mean she loves Wimzie any less. Later, she enlists "Dr. Wimzie," "Nurse Loulou" and the others to help her tend to Bo.

Yaya gives Wimzie some magical seeds that grow a plant that yields a special kind of flower. Jonas gives Wimzie some of his special dirt and they grow this plant together. When they see that the flower to be picked is a whistle (it's a Toot-Lip), each wants it for himself. They argue about who it should belong to: they're Wimzie's seeds, but it was Jonas' dirt. With Yaya's help, they finally come together to make a schedule about using it; they also understand that sometimes, these kinds of plans need to be made ahead of time to avoid disagreements. But then the Toot-Lip plant yields other whistles and there's enough for everyone, with the co-owners in charge of distribution...

Wimzie is feeling a little needy one morning and asks her parents to help her do little things like tie her shoes and pour a glass of milk. Rousso and Graziella are busy with Bo and remind Wimzie that she's a big girl and can do these things for herself. Wimzie then sees how Bo is catered to, and thinks that babies have it made. She kind of wishes she was a baby so she could benefit from the same treatment. At nap time she dreams she's turned into a baby. The experience, even in a dream, turns out to be not as great as she thought and when she wakes up, she has a new appreciation of what Bo goes through. She also realizes that she's pretty happy being the age she is.