Yoshi Topsy-Turvy

Yoshi Topsy-Turvy is the recovery of Yoshi's Island from its entrapment inside the Forbidden Pop-Up Book.

History
The Forbidden Pop-Up Book is an item that can trap things in its pages. It can only be wielded by Hongo, the great spirit of the book. He noticed Bowser recently rampaging in Yoshi's Island and decided to lock him away in his book. As a result, all of Yoshi's Island was trapped alongside Bowser.

Yoshi meets the Spirit Who Loves Surprises, a tiny book spirit, who explains what's happening and that he has to head to the last page of the book, manage to lock Bowser in another way, and have that convince Hongo to release Yoshi's Island from the book. However, to go to the next page, Yoshi has to appease the spirits in the book enough to allow him to move forward. As a gift, the Spirit Who Loves Surprises gives Yoshi the ability to tilt the world.

Yoshi continues to meet the Spirit of Cuteness, who explains that Bowser has chased her Egglings all the way to Yoshi's Island, where he turned them into apples. If Yoshi eats these apples, they return back into an Eggling.

Afterward, Yoshi sees the Spirit of Money, who wants money. Yoshi gets him money. The Spirit of Power wants Yoshi to prove his might by defeating a number of enemies. The Spirit of Speed wants Yoshi to clear a level within a set time limit.

After continuing a few pages, Yoshi expected to meet Bowser, but it was a cardboard cutout puppeteered by the Spirit Who Loves Surprises. Yoshi's angry, but continues to then meet the Spirit of Kindness, who doesn't want Yoshi to harm any enemies. Yoshi braves on and meets the Spirit of Fright, whose idea of scary is a wall of spinning blades that threatens to kill Yoshi if he doesn't move fast.

Yoshi then encounters the real Bowser and they both battle. Bowser is trapped in another way and swears revenge. Hongo thanked Yoshi with an extravagant meal, but Yoshi was not amused. Hongo realizes why and hurriedly returns Yoshi's Island back to its original state.

Timeline

 * Yoshi is living on Yoshi’s Island, placing this game prior to games where he resides in the Mushroom Kingdom.
 * Bowser is surprised to meet Yoshi here, suggesting that this may be their first encounter since Yoshi's Story.
 * Bowser takes over Yoshi’s Island but is beaten by Yoshi and sealed in a book. Bowser vows revenge on Yoshi, which serves as a motive for what Bowser does in Super Mario World and Tetris Attack.