In Kirby's Toy Box - Cannonball, the player controls a giant robotic Rick, which can shoot spherical Kirbys out from its head. The game is a simplified take on the same concept used by numerous other games based around lobbing parabolic projectiles at opponents over hills with destructible terrain, such as Scorched Earth and the |Worms series. A large hill divides the screen into two halves, with Player 1 on the left; the right side is occupied by another robot hamster, which is controlled by a CPU or a second player. The goal of the game is defeat the opponent robot by hitting it with enough Kirbys. Each robot can move its head to change the direction and angle of the Kirbys it fires. They can also walk slowly forward and backward. The robots can blast tiny holes in the hill by shooting it with Kirbys. When one robot is defeated, the game ends with surviving robot being the winner.

There are multiple stages to play on, but the only difference between them is the scenery. Clouds will stop any Kirby that hits them, causing the projectile to lose all momentum and fall.

Like every other sub-game in Kirby's Toy Box, this game could only be downloaded by the Satellaview during the brief period it was broadcast.