Tiny spirits
The Yoshi Island Spirits have only appeared in Yoshi Topsy-Turvy to date. Each had a special objective to be cleared before they let Yoshi pass. Their leader appears to be Hongo.
It is unknown if the Spirits have a hierarchy of power among them, or if they reside or have resided anywhere but Yoshi's Island, which is where they currently inhabit. The Spirits include:
Hongo, the Book Spirit
Hongo is the leader of the Yoshi Island Spirits. He is firm and elderly but shows he can be forgiving at times.
Spirit of Cuteness
The Spirit of Cuteness looked like a balloon with wings. She cared about the Egglings and wanted Yoshi to save them.Yoshi had to eat apples to transform the apples back to egglings.
Spirit of Greediness
The Spirit of Greed looked like a golden mouse who had a pocket full of money. To pass him, Yoshi had to collect coins in the level. He had a golden shadow.
Spirit of Mightiness
Also known as the Spirit of Strength, and the Spirit of Mightiness, the Spirit of Power is the strongest of the spirits. He resembles a purple boxer. To clear his levels, the player must defeat a preset number of enemies, almost the exact opposite of the Spirit of Happiness.
Spirit of Scariness
More commonly known as the Spirit of Fright, the Spirit of Fright is a reanimated mummy spirit who's tasks involve unusual, frightening puzzles.
Spirit of Kindness
The Spirit of Kindness resembles a flower. Her tasks for Yoshi always involve killing the least amount of enemies in a level possible.
Spirit of Swiftness
Better known as the Spirit of Speed is a Spirit who loves to challenge others to races. She is competitive in a friendly way.
Spirit Who Loves Surprises
The Spirit Who Loves Surprises is a Spirit who was banished from the Spirit Council under the orders of Hongo. He assists Yoshi throughout Yoshi Topsy-Turvy and hosts mini-games.
Speculation
To date, the Spirits have only been in Yoshi Topsy Turvy but some hopeful fans suggest the Spirits could host a future Mario Part, similar to how the Star Spirits which were introduced in Paper Mario went on to be the guides of Mario Party 5. This is mere speculation and no such word has come in any form of an official statement from Nintendo therefore should not be taken seriously.