Challenges completed by BowserJr03
I couldn't find an image of the Hint Man on WikiBound, so I used the next best thing.
Fourside : Go see the Hint Mr. Saturn.

Falling in the Water
Fourside : Finish the game in less than 5s

Gettin' yo girl back
Fourside : Finish the game in the 1st position

B U P gets s m a c k e d
B U P : Finish the game with Toad, in less than 10s, with 100 participants

Coins in Mario Circuit
Mario Course 1 : Collect all coins in Time Trial mode, in less than 1:25

Waiiiiiiit Not that Fast !
/!\ Défis Vitesse 2 /!\ : Collect all coins in Time Trial mode, without touching any Piranha Plant

The Extreme Race
Mario Circuit 1 : Finish in the 1st position in VS mode, with 100 participants
In difficult mode, no teams

Finding Everdread...or rather, Everdead
Fourside : Collect all coins

...So where exactly do you fight in Smash?
Fourside : Go to every intersection.

Zigzag Boardwalk : Go through all 10 rings in order in Time Trial mode, in less than 45s

why do we exist?
baguette : Complete the track in less than 1:10 in Time Trial mode, without using any item

Encuéntrame...
Dragon Boy's Rest Valley : Encuentra mi cuerpo corrompido tras quedar atrapado en este videojuego... with King Boo

Coin Grubber
Thwomp Circuit : Collect all coins in less than 30s
With 8 participants

Sherbet Land : Collect all coins in Time Trial mode, without touching any Freezies, with Rosalina, in less than 1:00

is this my first battle challenge?
Survive more than 3:00 with 1 balloon or more, without drifting, without touching item boxes, without using any item

Sherbet Land : Complete the track in less than 1:40 in Time Trial mode

Coins in Battlefield
SNES Battle Course 1 Race : Collect all coins in Time Trial mode, in less than 3:00

Time trialer
a simple time trial course : Collect all coins

Survive!
Toadstool Titan a.k.a Mush Pit : Survive more than 1:00 with 4 participants

Classic Mario Party!
Toadstool Titan a.k.a Mush Pit : Finish the game in the 1st position with 4 participants
No teams
