Bowser Jr. Breakdown

Bowser Jr. Breakdown is a boss minigame featured in Mario Party 9. This and Bowser's Block Battle are the only minigames played on Bowser Station, and players cannot choose from three other boss minigames. The same thing happens on DK's Jungle Ruins.

Introduction
Bowser Jr. will fly down to the stage in his Koopa Clown Car. A larger version of the car, with two clawed arms sticking out of it, will then float down, and Bowser Jr.'s car will link up with the bigger one.

Gameplay
The starting player depends on the game mode being played. If battling Bowser Jr. on the Bowser Station board, the captain takes the first turn.

In Free Play, a "spinning" arrow decides who goes first.

Players try to defeat Bowser Jr. by rolling dice numbered 1-6 to fill the gauge at the top of the screen. Each number rolled fills that many spaces on the gauge.

If a player's roll fills the gauge to a multiple of three (or to 15 or above, as the gauge stops there), the player attacks and deals that much damage to Bowser Jr. Once a player attacks, the gauge empties. If the gauge is filled to 14 - marked by the Bowser Jr. symbol - the young Koopa will roll a die numbered 1-2 and smash the player with a hammer for the number of times indicated by the number rolled and making the player lose that many points. This does not empty the gauge, which means that a player unlucky enough to be attacked by Bowser Jr. also sets up the next player with a guaranteed 15 points.

When Bowser Jr. reaches half health, the larger car's eyes will change color from yellow to red, and Bowser Jr. will add two additional Bowser Jr. spaces to the gauge. The new spaces are randomly placed, but they never cover a multiple of three or a number lower than 6. Also, if a player's roll reaches one of these spaces, Bowser Jr. will roll two dice instead of one and strike the player with two hammers for that amount of damage.

This mini-game is solely luck-based, as the players don't have any control over the numbers that they roll.

Ending
When Bowser Jr. is defeated, his clown car explodes and Bowser Jr. himself is launched into space. Several Mini Stars then appear.

In-game text

 * Rules – "Hit the Dice Blocks. The number that appears will light up segments of the gauge at the top of the screen. Light specific segments of the gauge to deal damage to Bowser Jr."
 * Controls – "Hold the Wii Remote vertically. Press to hit the Dice Blocks. You can make the Dice Blocks spin faster by shaking the Wii Remote."