When Ball is used, Kirby becomes a perfect sphere and is able to roll and bounce around the level when the jump button is held, damaging anything he hits in the air. The longer he falls, the more force his bounce will have when he hits the ground.
Ball is a fast-moving ability and can be difficult to control when faced with a wall or cliff. On top of that, although Kirby is invincible when flying through the air, he is vulnerable both at the peak of his jump and immediately after he hits the ground, meaning he will take damage if he happens to land directly in front of a moving enemy (or lands right on top of a boss or invincible enemy like Shotzo). However, while it may be impractical when dealing with minor ground-borne enemies, the Ball ability's saving grace is, strangely, its sheer damage: it can destroy most of the game's bosses with a mere four hits, and mini-bosses (the ones that don't grab Kirby) with as few as two or three.
Also, in Kirby: Nightmare in Dream Land, Ball Kirby (when not in ball form) has a sort of a hat like Yo-Yo or Wheel, but not exactly alike and without a visor. Strangely, there is another design for this cap in the icon. Along with Hi-Jump, it was upgraded - the top of the screen is considered a wall and will not reset Kirby's momentum.
Kirby transforms into a smooth ball. While in ball form, he must roll or bounce to move.
When in ball form and bouncing, Kirby is vulnerable to grabs.
Kirby cannot be grabbed. Also, the top of the screen counts as a boundary when bouncing. To return to regular Kirby, press B again.
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.
Also, the ability icon shows Kirby wearing a wig. He never actually wears this when wielding the ability.
Kirby of the Stars Copy Ability "Ball" Introduction Video