Elline uses her power to turn Kirby into a powerful tank, which helps him advance over rough terrain. He can shoot at enemies using his mouth cannon, too! Just be sure to support him with a rainbow rope.”
When in this form, Kirby becomes a pink and orange tank with a red cannon for a mouth.
Kirby and the Rainbow Curse
Kirby can transform into Kirby Tank in the stages Deploy the Kirby Tank! and Woodland Battle. While in this form, the player can tap on the touch screen to aim and fire Kirby Tank's mouth cannon. When he collects 100 Point Stars, he is able to transform even further--depending on how long the player holds the stylus to the touch screen, Kirby can fire three, four, or eight shots rapidly.
This is Kirby Tank's most powerful form. He can unleash a brutal attack, but he needs a bit of time to recover afterward. That's why he can't take on a more powerful form when he's Kirby Rocket or Kirby Submarine.”
— Mega Kirby Tank's figurine description • Kirby and the Rainbow Curse
Tap the target to show Kirby where to fire his cannon.”
— Official Kirby and the Rainbow Curse website
While Kirby is being transformed into the Kirby Tank, Elline momentarily transforms Kirby into Rick the Hamster.
Kirby Tank's third form is the only one that does not affect his mouth.
Notes from the ESRB that explain Kirby and the Rainbow Curse’s E rating explicitly mention Kirby Tank, saying: "As players traverse side-scrolling levels, they can transform into various vehicles (e.g., tanks, submarines) that fire projectiles at enemy creatures."