The imagination of a wildly creative girl comes alive in an amusement park.

June, an optimistic, imaginative girl, discovers an incredible amusement park called Wonderland hidden in the woods. The park is full of fantastical rides and talking, funny animals - only the park is in disarray. June soon discovers the park came from her imagination and she's the only one who can fix it, so she bands together with the animals to save this magical place and bring back the wonder in Wonderland.—Wulf97

June Bailey and her mother come up with the story of Wonderland, a magical amusement park run by animal creatures that entertain and dazzle children of all ages. The gang consists of Boomer, a big blue bear that greets patrons; Greta, a boar who manages and keeps things under control; Gus and Cooper, beaver brothers; Steve, a porcupine who is in love with Greta; and the park's mascot/leader Peanut, a monkey who hears Mrs. Bailey's voice and is given the inspiration to create with his magic marker.

As June gets older, her imagination grows. She and her friend Banky create a contraption that functions like a theme park ride, but it goes out of control and causes massive damage to the town. June's parents scold her, but her mom tells her she can keep her imagination going as long as it doesn't destroy the neighborhood.

Over time, the family continues to have fun, but Mrs. Bailey starts to get sick. She is sent away for recovery, leaving June scared and depressed. She starts to become cynical and refuses to play with the other kids because she thinks they only care about her giving them Wonderland. June and her father are then visited by Uncle Tony and Aunt Albertine. They try to cheer June up by sparking her imagination with talk of Wonderland, but June snaps and throws out the map of Wonderland into the fire before running to her room to cry.

Mr. Bailey gets ready to send June to math camp with Banky and their other friends. Barely ten minutes into the bus ride, June becomes paranoid that her father will not be able to handle himself without her, so she uses Banky to create a distraction on the bus and get them to pull over. June uses the opportunity to run back home through the woods. She then finds a burnt piece of the Wonderland map flying toward it. June chases after it as it takes her deeper into the woods, and she finds herself in a completely different place. She steps inside a rocket ride and is transported into Wonderland before her very eyes...or at least, what used to be Wonderland.

When June gets down to the park, she finds the animals all fleeing in terror from a dark storm cloud. Emerging from it are Chimpanzombies, formerly the park's Wonder Chimps now becoming terrible troublemakers. The animals run and evade the Chimpanzombies. June introduces herself and tells the animals that she and her mom are responsible for creating them. Greta seems to be suspicious of June being there, but she proves what she knows about them due to naming a very specific way that Steve drinks his tea. June asks them what happened to Peanut, and they tell her that he went off on his own to reactivate Clockwork Springs to bring the park back to life, but he was captured by the Chimpanzombies.

June leads the animals to Clockwork Springs to help fix it, but she doesn't seem to know what she is supposed to do. The Chimpanzombies then attack once again in a giant robot that wreaks more havoc across the park. In the chaos, June gets separated from the animals and finds herself in Zero Gravity Land. There, she finds Peanut hiding in a room he created to escape the darkness. He feels lost without hearing the voice in his head and he chooses to stay alone so that he can't get hurt. This leads June to realize that the darkness was created by herself as a result of her cynicism from her mom's sickness. The Chimpanzombies then show up and attack once again and take Peanut as their prisoner, but June manages to escape with Peanut's marker.

June runs back to the animals to tell them that she found Peanut and his marker, but also confesses that she is responsible for the darkness. The animals are all upset, but Greta is especially displeased. They abandon June and leave her alone and helpless. After taking a moment, June gathers the courage inside her to reactivate her imagination and get a robot up and running to join the animals to help them. As they come up with a plan to stop the Chimpanzombies, they put Boomer on top of a roller coaster. His car gets pushed over by a bird, leading him to roll down the roller coaster without safety. The other animals manage to get him to come to a stop.

The gang finds the Chimpanzombies taking Peanut to get sucked up into the darkness. The animals fight back while June rushes to save Peanut. She jumps up into the void and reaches Peanut. She convinces him that she will provide the voice for his imagination and that he cannot let the darkness take him over. June gives Peanut an idea for making a slide to get them out of there. As they slide down, June then notices Clockwork Springs is her name written in cursive, just like on the piece of her map. With Peanut's help, they get Clockwork Springs back up and running, which gets rid of the darkness, brings Wonderland back to life, and makes the Chimpanzombies turn back into regular Wonder Chimps. Children then start coming back with their families and are in awe of the animals. The animals welcome Peanut back as their leader, but he says that Greta did a good job leading them. They look up to the sky and see the cloud is still there, which June interprets as meaning that while the darkness may never really go away, it is there to remind us to look on the bright side. June says farewell to her animal friends before returning to the real world.

June runs out of the woods and goes back home to her father, now with more spirit and vigor than before. She and Banky then get together to create more things to make a real Wonderland. There is then another knock at the door, and Mr. Bailey tells June she should get the door. He opens it, and Mrs. Bailey comes inside, now feeling all better. June jumps into her mother's arms.

The Baileys then unveil the real Wonderland in their backyard, which is big enough to have all the neighborhood kids show up. June starts to tell the kids a story about Wonderland, and she takes a doll of Peanut and whispers an idea into his ear. In Wonderland, Peanut hears the idea, and he takes his magic marker to make the idea come to life.