They are unlockable in the Shop:

Effect - Code

Bowser's Crazy Torch - Pay 500 mileage points
Bowser's Killer Cannon - Pay 500 mileage points
Bowser's Boiled Eggs - Pay 500 mileage points
Cheep Cheep Fountain - Pay 500 mileage points
Blooper Fortune-Teller - Pay 500 mileage points
Grand Canal Cookies - Pay 500 mileage points
Gong Clock - Pay 500 mileage points
Fuzzy Sheep - Pay 500 mileage points
Windy Cheese - Pay 500 mileage points
Kung Fu Koopa T-Shirt - Pay 500 mileage points
Sticky Buns - Pay 500 mileage points
Pyramid Piggy Bank - Pay 500 mileage points
Ancient Jar - Pay 500 mileage points
Desert Chocolate - Pay 500 mileage points
Model Rocket - Pay 500 mileage points
Mysterious Flying Disc. - Pay 500 mileage points
Top Hat Chocolate - Pay 500 mileage points
Model Windmill - Pay 500 mileage points
Kung Fu Kooopa & Koopa Sheperdess - Pay 500 mileage points for each one
Desert Goomba & Steel Goomba - Pay 500 mileage points for each one
Singing Shy Guy & Hop Hat Shy Guy - Pay 500 mileage points for each one