Giant Kirby is fought on Stage 5 of Adventure upon the Green Greens stage as an optional boss. If the player manages to defeat the team of Kirbys in 31 seconds or less, a cinematic will play where Giant Kirby drops onto the second floating platform and lands crouching before standing up and smiling.
Giant Kirby is slightly larger than a regular Kirby with a Super Mushroom and is heavier and stronger than Kirby. If the player defeats Giant Kirby, they will receive the bonus "Giant Kirby KO", which awards 10,000 extra points.
Kirby is one of the characters who may be encountered in a Giant Battle in Classic Mode:
Giant Kirby (in an alternate costume resembling an unmasked Meta Knight) is fought on Kalos Pokémon League in Round 2 of Joker's Classic Mode route with Mr. Game & Watch serving as the latter's ally against the former. Giant Kirby is also the only opponent in Joker's route to be fought on a stage other than the latter's home stage Mementos.