This guide will help you find all the 5 secret characters hidden in the tracks. To Unlock them, you must find a key and get in the top 3 karters. Note that it is possible to find them in free play, making the task easier.
Terry Trash Dome
This key is found early in the track
Hint 1: It is located in the Zone where you go down a long slope
Location: If you go down early from the slope and check behing you, you should find the key
This one is tricky too find, it follows the same rule as a Mario Boo mansion!
Hint 1: One of the walls is a fake one
Hint 2: It is located in the room with the minecarts coming out of the paintings, the green room
Location: At the right, right bellow the torch is the fake wall location
Sleazy Alley
You might want to find a back alley for this one
Hint 1: When the road forks and gives a descision between right and left, take left
Location: After taking the left side, jump on theramp and pass the wall inside a little car lot, it will be sitting on a truck. You can also find a alley leading to it towards the right if you miss the jump
The Beach
It took me the longest to find this one! It is NOT in one of the huts XD
Hint 1: It is next too a long beach chair
Location: The beach chair is right after a slope, to the left
The forest
If you very lightly stray from the normal path, you might find it!
Hint 1: The location is the room with the big pillar you can boost on
Hint 2: It is located behind a rock
Location: Behind a rock on the right side, very early in the pillar room