Ball focuses on bouncing to increase its kinetic energy to deal damage. Ball allows Kirby to transform into a perfect sphere and is able to roll and bounce around, although its rolling and bouncing can also make controlling it difficult. As the Ball ability focuses on ramming into enemies to deal damage, it uses invincibility to prevent from taking damage itself; however, Ball is only invincible when it is traveling fast enough from a bounce, making it vulnerable during the crests and troughs of its jumps. While risky, Ball is very powerful when used carefully. Ball can be obtained from the Bubblesenemy or Paint Roller's baseball painting; Ball is also available in Grape Garden's Museum, which is unlocked by pressing the Big Switch in Stage 3.
In Kirby: Nightmare in Dream Land, Ball Kirby can bounce off ceilings, making it generally safer to use in areas that have them, including ones that do not scroll vertically.
Kirby transforms into a smooth ball. While in ball form, he must roll or bounce to move.
Kirby returns to normal.
A while transformed
When Kirby lands from a jump, he will bounce up a great distance. Landing consecutively will allow Kirby to bounce even higher, although it does have a limit to its height. In Kirby's Adventure, Kirby is still vulnerable to grabs in this state, but in Kirby: Nightmare in Dream Land, he is not.
Kirby can roll into a smooth ball! If you hold the A Button, he will jump higher!
Change form and Hold the A Button! BOUNCE! BOING! BONK!
When Kirby swallows a ball enemy, he turns into a ball and can bounce off of floors and walls. It's tough to control, but well worth it for the strong attack power it gives Kirby. After his debut in Kirby's Adventure, Ball Kirby has popped up in several more Kirby games, such as Kirby's Pinball Land and Kirby's Block Ball.”
What appear to be the American and Japanese flags are depicted on Ball's ability icon in Kirby: Nightmare in Dream Land, giving it resemblance to a Gymnastic event, where the flags of the various nations competing are often displayed as part of the arena.
Kirby of the Stars Copy Ability "Ball" Introduction Video