Bumper Sparks

Bumper Sparks is a Bowser Jr. minigame in Mario Party 9. Bumper Sparks is most likely a pun on bumper cars, a fairground activity. This is also like the minigame Bumper Balls, which is found in Mario Party and Mario Party 2

Introduction
Bowser Jr. runs into his Clown Car and turns around to face the camera. The camera then zooms out to show the entire playing field.

Gameplay
The pair must try to knock Bowser Jr. into the electric fence three times before time runs out. Players will bounce off of each other and Bowser Jr. If a player hits the fence, they will be stunned temporarily, but if Bowser Jr. hits the fence, he loses a heart and returns to the center, temporarily invincible. Bowser Jr. generally does not try to attack the players, but will sometimes lead them into the electric fence. If the pair fail to knock Bowser Jr. into the fence three times in 30 seconds, Bowser Jr. is victorious.

Ending
If the players are victorious, Bowser Jr. and his Clown Car go flying off the screen.

Trivia

 * This is very similar to the boss battle against Topmaniac in Super Mario Galaxy, and is almost identical to the battle against Bowser Jr. on the second airship in New Super Mario Bros. Wii. Also the sound played during this battle is a slowed down version of the original.