Andy and Terry live in a 91-story treehouse. (It used to be a 78-story treehouse, but they keep getting ideas for new stories!) It has a submarine sandwich shop that serves sandwiches the size of actual submarines, an air-traffic control tower, a human pinball machine, a spin-and-win prize wheel, a giant spider web with a giant spider! and a big red button, which they are not sure whether to push or not because they can't remember what it does. Good...

Having expanded their treehouse to an astonishing thirty-nine stories, Andy and Terry describe the invention of their "Once-Upon-a-Time machine," which they have designed to write and illustrate their stories for them.

The magic tree house takes Jack and Annie to Africa where they meet up with wonderful wild animals, a very hungry warrior, and where they even solve a riddle.

"Andy and Terry live in a 143-story treehouse. (It used to be a 130-story treehouse, but they built another thirteen stories.) Andy's been a bit stressed out lately, so Terry decides the perfect way to relax would be to head up to their new camping ground level for a much-needed vacation. But it turns out to be not quite as relaxing as planned. Terry forgets to pack the tent and the food, their attempt at fishing ends in disaster, the spooky campfire...

Andy and Terry travel through time trying to save their treehouse from highly talented, angry ants and Inspector Bubblewrap the building inspector while rushing to meet their publisher's deadline.

When strange noises are heard in the tree house where their club meets, Claire and Kaz wonder if a rival club is causing problems in order to scare them away, or if they are coming from the ghosts of one of Kaz's departed ancestors.

Fairies Mip and Pip challenge each other to see who can build the tallest tree house by sundown, but a terrible storm soon threatens their competition.

Jack and his younger sister take a trip in their tree house back to ancient Egypt, where they help a queen's mummy continue her voyage to the Next Life.

When Andy develops a severe toothache that prevents him from writing new jokes for their book, Terry uses their fantastical treehouse's money-making machine funds to purchase a Joke Writer 2000, with unexpected results.