Challenges completed by Army
Don't get Thwomped!
Blue, Blue Plaza : Go under a Radioactive Thwomp.

Get to the other end of the Arena
Blue, Blue Plaza : You'll find this area on your own. If you need a hint, check the title.

Yeah
The Real End : Drive straight for about 10 seconds in Time Trial mode

Monty Mole Trench : Complete the track in less than 2:05 in Time Trial mode, without falling

Monty Mole Trench : Complete the track in less than 2:40 in Time Trial mode, by falling at most 3 times

Not a challenge
Metal Arena : Go to any of the Cannon Ramps with King Boo

...so shy...
Metal Arena : Go in the middle of the Ring of Item Boxes with Shy Guy

Whatever You Do, Don't Drift!
MKSC Mario Circuit 1 (SNES) : Complete the track without drifting

1st Place Action!
MKSC Mario Circuit 1 (SNES) : Finish in the 1st position in VS mode

Firmly Grasp It!
Jellyfish Fields : Get to where you would fight King Jellyfish.

Ouch! That's cold.
Super Dooper Stadium 2 : Go in the center of the Ice, with Rosalina

Race through the Rings
MKT Rock Rock Mountain T : Find the rings in Time Trial mode, with 1 participant, with King Boo

Yoshi needs to win 1st or no cookies
SNES Donut Planis 1 (GBA) : Complete the track in less than 2:05:864 in VS mode, with 4 participants, in 1st place, with Yoshi

Time Trial Decetive
MKT Yoshi Circuit : Reach to the Yoshi Tunnel in Time Trial mode, with Daisy

Bowser Jr wants a Job
Silverstone Circuit 10 : Find Mr. Krabs next to the Cheep Cheep in Time Trial mode, with Bowser Jr

The Backyardigans
Haunted House : Enter The Haunted House in VS mode

Stroll through Toad Town
Toad Town : Complete the track in VS mode, with Toad

Okay Formula Racer
Formula Circuit : Complete the track in less than 2:00
With 8 participants

Good Formula Racer
Formula Circuit : Complete the track in less than 1:45
With 8 participants

Master Formula Racer
Formula Circuit : Complete the track in less than 1:20
With 8 participants
