Literature: The Magic Treehouse aka: The Magic Tree House
This book inspired a plethora of equally outrageous adventures.
The Magic Treehouse is a successful series of children's books written by Mary Pope Osbourne. There are over fifty books in the series so far, not counting the research guides that go along with them. The books are about two kids from Frog Creek, Pennsylvania, siblings/kid heroes Jack and Annie. In the inaugural series, Morgan le Fay orders them to go on missions through time and all around the world to solve ancient riddles, save ancient stories, and become Master Librarians. That was for the first 28 of the books, and the next series was about Jack and Annie going on Merlin Missions (missions directed by Merlin the magician), traveling to places like Camelot. The books teach kids about history and the different cultures that Jack and Annie visit.There's also a Japanese adaptation with Mangaillustrations. They all contain paper dolls of Jack and Annie with outfits corresponding to the stories. The first 28 volumes were published into 14 Japanese volumes, two stories to a book. After that, each book was published individually. There was also an anime movie by Ajia-Do based on the book series.As of August 2012, nonfiction companions called Magic Treehouse Fact Trackers books have been written for 27 of the original series.
Animorphism: Teddy the dog is actually a human boy who accidentally put himself into a spell by mistake. Also, Morgan spends four books as a white mouse due to a prank pulled by Merlin.
Jack and Annie also get into this too. They were transformed into ravens along with Teddy in Haunted Castle on Hallow's Eve and were turned into dogs in Dogs in the Dead of Night. Annie also transformed two rival wizards into ducks in Blizzard of the Blue Moon.
Arbitrary Skepticism: Annie is afraid to enter an Old West ghost town. Jack attempts to reassure her by saying there's no such thing as ghosts, but as she points out, this is clearly untrue, as they met one in ancient Egypt.
Bears Are Bad News: Subverted in Stage Fright On A Summer's Night. The dancing bear's actually one of the nicer characters.
Averted in Polar Bears Past Bedtime with a mother polar bear and her adorable cubs.
And briefly discussed in Haunted Castle on Hallow's Eve.
This is averted in Good Night For Ghosts with Louis Armstrong. He has no clue about it and is just too busy making money for his family. After using the Wand of Dianthus and Louis having no sense of what to do next, Annie tells Jack that they actually have to show him the book that teleported them to his time to set things straight.
Alexander Graham Bell, Thomas Edison, Louis Pasteur, and Gustave Eiffel from Night of the New Magicians seem to think that Jack and Annie are crazy. They're nice about it, though.
Perfect Time For Pandas has got to be an ironic title, considering that Jack and Annie were transported to the time of the Great Sichuan Earthquake of 2008. The Result? Only 2 out of 16 roly-poly pandas in the reserve that they traveled to live.
Brick Joke: In books 32-36, Annie and Jack are given a book of spells from their friends. Annie is constantly trying to find a use for the spell 'Turn People into Ducks', but is constantly turned down by her brother. When they are trying to save a unicorn in Blizzard of the Blue Moon from two apprentices of a dark wizard, she immediately uses the spell, explaining that she memorized it a long time ago.
Bully Hunter: Annie in Twister on Tuesday when her brother is being picked on.
Cats Are Magic: Mummies in the Morning has a cat that leads Jack and Annie to a pyramid, and successfully leads them out of one. It's revealed in the next book that this was Morgan looking after them.
Exact Words: In Blizzard of the Blue Moon, Jack and Annie need to call out the name of a unicorn known as 'Divine Flower of Rome'. Unfortunately, the poem didn't state that the two had to say his name in Latin — which is Dianthus — and thus got them into a bit of trouble later on.
Exty Years from Now: Midnight on the Moon takes place 40 years in the future (the book was made in 1996, so it takes place in 2036).
Foregone Conclusion: In Earthquake in the Early Morning, Jack read that many of the books that were being transferred were all going to burn... unfortunately, the librarian didn't listen to him...
Four Is Death: Each arc is made out of 4 books together, and something happens within each one of them. Most notably is arc 21-24, which has, in order: Civil War, Revolutionary War, Twisters, and the San Francisco Earthquake.
Free-Range Children: The trope is averted by having no time pass — or at most ten minutes — while the treehouse takes the eight and seven year old to anywhere they want.
Friendly, Playful Dolphin: In "Dolphins At Day Break," Jack and Annie are saved by friendly dolphins that allow Jack and Annie to ride them.
Invisibility: The supposed ghosts in Haunted Castle on Hallow's Eve are actually three kids and their dog trapped in their state because the Raven King stole the Diamond of Destiny they were supposed to guard.
Kangaroo Pouch Ride: Inverted in Dingos at Dinnertime. The Joey hops into Jack's backpack believing that it's a pouch.
Not Allowed to Grow Up: Averted. It seems this way, as we are constantly told that Jack is 7 and Annie is 6. But in Winter of the Ice Wizard, Annie states that she's 9 and Jack is already 10, which means at most 3 years have passed since that time.
Oh Crap: Whenever something bad happens, poor Jack will be thinking this.
Unfortunately, they can't change anything that will happen (Pompeii and Titanic are prominent examples), but they can alter some minor details. In Civil War On Sunday, they save a drummer boy who would become their great-great-great grandfather, and Earthquake in the Early Morning had them be taken in a photograph with a piece of wood that had words of hope on it.