A new festival of battle is about to begin! Test your limits with...The Ultimate Choice! Kirby and friends will face off against a gaggle of super-spicy bosses in their unending quest to gobble up everything in sight!”
— The Ultimate Choice Pause Screen Description • Kirby Star Allies
The Ultimate Choice is a sub-game in Kirby Star Allies similar in concept to The Arena sub-games from previous games in the Kirby series. This one is different from The Arena sub-games, as the player can select the difficulty. Although five difficulties are available by default, there are four extra difficulties that can be unlocked. Completing Guest Star ???? Star Allies Go! once and completing The Ultimate Choice once unlocks Fiery Showdown and Infernal Crisis difficulties, and completing The Ultimate Choice once on Fiery Showdown or Infernal Crisis unlocks the Soul Melter difficulty. Completing The Ultimate Choice once on Soul Melter, as well as completing Heroes in Another Dimension once, unlocks the Soul Melter EX difficulty.
The player can select Kirby without an ability, a Copy Ability, or a Dream Friend; pressing X when selecting a Copy Ability will allow the player to become the Friend instead. The player can also add up to three more friends, which can be controlled by other players or CPUs. Before starting and after every round, Kirby and his friends will be taken to the rest area, with six Maxim Tomatoes that get replaced by regular tomatoes when used. On higher difficulties, some of the Maxim Tomatoes get replaced with Pep Brews, one for each extra difficulty level, culminating in six Pep Brews at Infernal Crisis. Treasure chests containing Picture Pieces appear after defeating a boss.
If playing on the Soul Melter difficulty, all healing items will be replaced by regular tomatoes, and if playing on any of the last three difficulties, maximum stamina is reduced, even more so at the Soul Melter difficulty. The player can still use amiibo to get picture pieces and food items in the rest area or during battles (except when they are on the Star Allies Sparkler). However, like in Kirby: Planet Robobot, using amiibo functionality even once will put the amiibo insignia next to the player's clear score after completing The Ultimate Choice.
If playing on Soul Melter EX, maximum stamina is the same as in the first four levels of difficulty, unlike the previous high difficulties, and healing items will be two of each three foods: Maxim Tomatoes, regular tomatoes and Pep Brews.
The higher the difficulty level, the more points are awarded for clearing The Ultimate Choice. Completing Soul Melter EX unlocks the option to change Kirby's appearance to his original design (used from Kirby's Dream Land to Kirby Tilt 'n' Tumble).
Depending on the difficulty, what bosses will be faced and how many bosses are fought will vary. All bosses are fought in the same order on each difficulty setting and each difficulty adds more bosses onto the order. This linear concept carried over from Kirby: Planet Robobot. The rest area starts out in a beige room similar to the Dream Palace, but as the difficulty rises it can eventually transition into a fiery, darker setpiece. If playing on Soul Melter EX, the rest area is first shown as the dark variation seen on the last four difficulties, but as the fights progress, it transitions to an even darker, decrepit scenery, with a visible hole in the wall showcasing red, black and green skies.
The face Kirby makes while highlighting the Soul Melter difficulty is a reference to the Kirby: Right Back at Ya! episode Frog Wild, where it matches the possessed Kirby's expression.
Grand Mam is the only boss that appears in Story Mode that does not also appear in The Ultimate Choice.
The hot sauce bottle used to increase the sub-game's difficulty has the Jambastion insignia on it.
Before unlocking Fiery Showdown/Infernal Crisis, the color scheme of the sub-game's logo is primarily orange. Before unlocking Soul Melter, it becomes primarily red. After unlocking both, it changes to primarily black.
On Soul Melter difficulty, certain boss themes are replaced by other themes from the series:
After clearing The Ultimate Choice, a message, which varies depending on the difficulty chosen, will appear proclaiming the player's victory:
Sweet Breeze through Sizzling Threat: Victory!
Fiery Showdown through Infernal Crisis: Huge Victory!!
Soul Melter: Incredible Victory!!!
Soul Melter EX: Truly Incredible Victory!!!
Through Sweet Breeze to Infernal Crisis, the fanfare that plays in the victory screen is a snippet of Friendly Field's background music. On Soul Melter EX, this fanfare is replaced with the Title Theme from Kirby's Dream Land.
The "intensity gauge" setup of The Ultimate Choice is very similar to the custom difficulty modifier systems in Kid Icarus: Uprising and Super Smash Bros. for Nintendo 3DS and Wii U. It further mimics these games by showing increasingly infernal and more threatening visuals on the difficulty selection menu as the level is increased, with the hardest options appearing completely demonic. In this way, Kirby Star Allies can be considered the first Kirby series game to show distinct influence from games directed by Masahiro Sakurai that were made after his departure from HAL Laboratory.
Kirby is only allowed to throw Friend Hearts in this sub-game during the battles against Morpho Knight, Void Termina's heart, Void Soul, and Void as they can be used to recover friends who are bewitched by these bosses' powers.
The code used to unlock Soul Melter EX is the same one that was used in Kirby's Dream Land to unlock Extra Mode.
On the Soul Melter difficulty, when Kirby's health is depleted and no one revives him in time (multiplayer only), the jingle from Kirby's Dream Land will play instead of the usual jingle.
Upon clearing Soul Melter EX, a "Dream Button" is added to the main menu. When activated, Kirby's appearance changes to that of his original Kirby's Dream Land appearance.