George is a huge fan of the Mexican family band Lobos de la Plata when they play in the park's old bandstand. But when the old bandstand is torn down, George and his new friend Marco must find a new place for the band to play, but every place they try makes the band seem to sound awful. In the process they learn all about acoustics and how things such as a carpeted floor and a high ceiling make things sound different.

It is George's first day of spring on the Renkins' farm and he and Bill arrive on the farm just in time to see Dumpling, the Renkins' duck sitting on her eggs to hatch them. But when she leaves and George sits on the eggs in her place, one of the eggs hatches and the duckling thinks George is its mother. George needs to try to get the duckling to see its real mother.

George gets to meet Mr. Zoobel's newest pet, a chameleon! Mr. Zoobel tells George that the chameleon has a unique ability: she can change her skin color to blend in With her surroundings. After she breaks out and George cannot find her, he thinks she may have changed color to blend into her hiding place.

George is in for a surprise—he and the Man With the Yellow Hat are going to the zoo to see a Komodo dragon and they are going to ride the subway to get there! Along the way, George and The Man get separated and they have to get back together before they reach the zoo. Meanwhile, George learns all about how the subway operates and how it gets people between places.

George is outside watering the garden when he gets muddy. He tries to take a bath but there's no water. Not even in the sink. Mr. Quint explains that they have a broken pump. And then he explains how to get the water, with a well and a pump. The pump they have is old. Then The Man explains that an electric pump sends it through a pipe to the house. And they go back to the city since it'll take days to get a new pump. When the go to the apartment, they don't see an orange flier. It says the plumber must shut off the water now. This means there's no water here, too. So George tries to get more water with a pipe.

George loves cars And when he hears about the annual Soap Box Derby race in the country, he and Allie decide to enter. But first, they need to build a car, and the rules say no help is allowed. So they look at a book that shows them the parts they need to build a soap box derby racer and find out just what is needed to make one go downhill, and stop.

George is off to one of his favorite places in the city, the library. But when Mrs. Dewey the librarian has to run off, she leaves him in charge of the library to stack and sort books. When George has trouble finding a certain book, he decides to rearrange them, first by color, then by size. But then Steve tells him that the proper way to arrange books is by subject.

It's The Man with the Yellow Hat's birthday and George wants to throw him a surprise party. The Doorman tells him what he needs to throw a good party, which includes cake, decorations, and friends. But George picks the wrong sizes for everything which leads to disaster. Then George has a dream about what the world would be like it if were monkey-size and decides that in a people-sized world, it is simply a matter of measuring to find the right size.

George and the Man are staying at Professor Wiseman's beach house and George has his favorite toy: Yorbo the Robot. But after taking it outside, it gets buried under the sand in a sudden thunderstorm and George wants to find it. He has trouble trying to find it on the huge beach, until a lady comes and shows him a metal detector. But when George cannot use hers anymore, Professor Wiseman shows him how to make one out of an FM Radio and a calculator.

At the museum, George discovers something he has never seen before-a vending machine and becomes curious as to how one works, thinking there is a farmer and an apple tree inside an apple machine. But then someone shows him what is really inside, a series of simple machines. The Man is asked by Professor Wiseman to host a party for two expedition groups at his apartment and leaves George in charge of dessert. So George decides to build his own vending machine to make it.

At the annual Spring fair in the country, George and Allie come across a sheep shearer and a family making yarn out of a sheep's wool. They also come across a sheep herding contest where Mr. Renkins commands his dog, Bo with a special whistle to herd sheep. When they return home to the country house, the scarf George bought from the yarn makers begins to unravel and they need someone to fix it, but Jumpy Squirrel steals the yarn leaving them in search for more. It seems all of the Renkins' sheep were sheared at the fair and they begin to escape the pasture! George sees the whistle Mr. Renkins used to command Bo and uses it to command Bo to stop the sheep from escaping but is not sure how.

George gets to see his very first baseball game! Marco and his team the Cubbie Bears are playing in the city against the Tiger Babies. But when the scorekeeper can not make it to the game, Marco leaves George in charge of keeping score. The only problem is, George does not know how to count! Marco tells him how to count and makes him remember with a simple song. Later, though, George is also left in charge of the baseball park snack bar and he sees numbers higher than 10.

In a sunny but snowy winter day in the country, George comes across Bill building an igloo in an attempt to earn his newest Sprout Badge. Bill tells him that to earn the badge, he will build an igloo and spend the night in it. George decides he would like to build an igloo of his own but he would like to make it big enough for all of his friends. Bill reminds him that smaller igloos hold more heat in but George remembers several thing Bill had done to make his igloo airtight. George builds a larger igloo but does not make it airtight, and he winds up freezing in the middle of the night. So he decides to build another igloo inside the house.

The Doorman orders a western town for his train set and Steve, Betsy, and George offer to help him put it together while he's at work. Hundley supervises. When the group accidentally sends a small pin from the train track into one of the plant pots, they must dump out all of the soil to search for the missing piece. Hundley falls asleep and dreams of himself and the group in a real western town. In his dream, George finds out how to make proper sifters to efficiently search for small objects, but in the end Hundley's sneezing is the secret to finding the pin. Reference: spaghetti western.

The Man in the Yellow Hat is busy preparing for dinner with Professor Wiseman, so he sends George to fetch some groceries for him. On the way, George realizes that their usual grocery store isn't open, but a new grocery specializing in Vietnamese food has opened across the street. George finds fruits and vegetables that are similar to the ingredients on his grocery list, but when he takes them home, he finds that they don't work in The Man in the Yellow Hat's recipes. George gets a tour of the store from the store owner's daughter, Mei.

George is very impressed by the model papyrus boat that Steve has built for history class. Steve wants to find a way to test the boat out but when he is unable to in the museum he decides to go to Endless Park. But a stray current caused by a rainstorm sends the boat on its way down the river and down a storm drain. Steve and George try to find the boat at the local waste treatment plant but due to the recent storm, the boat has completely bypassed the plant and floated out into the ocean. There, the waste treatment facility uses a skimming boat to collect floatables-trash that people have dumped into the ocean. They decide that Steve's boat may be floating in the ocean somewhere.

George is busy planting food in the rooftop garden of the apartment building but he has a problem. He can't stop Compass and his pigeon friends from eating all the seeds. He recalls how the Renkins built a scarecrow in their garden to scare away birds so he decides to do the same thing. But his is not scary enough to scare away any birds. Later, he and the Man with the Yellow Hat go to a farm in the country where George comes across a windmill. The farmer tells George that windmills can be used for many different things and they are all done with nothing but the power of the wind. So George decides to build a windmill of his own to make his scarecrow move. Reference: Don Quixote and the windmills.

It is nearing Mother's Day in the city and Marco decides that he should throw his mom a fiesta complete with a homemade piñata. He and George try to build one out of papier-mâché but Marco forgets it takes days for it to dry. Then George decides that they can build one out of empty food containers. But Marco and George have trouble trying to get a piñata that is shaped like a donkey.

When George sees a cricket at the annual country gymnastics competition he decides to follow it across the gymnastics obstacles because, being a monkey, he is very good at jumping and swinging. When Mrs. Somersault the area gym teacher sees George, she decides to sign George and Allie up for her gym class, which Bill also agrees to join. While they all enjoy her gym class, they are disappointed to find out that it only takes place once a week. So, they decide to build a gym of their own in the back yard of the country house, where they can practice when it is not gym class day.