Coins are collectible items in Wonderland. They come in many forms.
Classic Trilogy Coins
Key Coins appear in Wonderland Secret Worlds. They behave exactly like the rainbow coins do, but they have an image of a key shown on them instead of rainbow colours.
Bonus Coins appear in every game of the Classic Trilogy. When collected, they give the player 250 extra points. They are not required to beat a level.
Gold Coins appear in every game of the Wonderland Adventures Trilogy. They can be collected and used to buy items from merchants. They are not required to complete an adventure.