Mario and Princess Peach first find Huey in 3D form as a seemingly inanimate object in the inactive Prisma Fountain at the town square of Port Prisma. After Mario whacks him with his hammer, however, he wakes up and gets mad at him for hitting him while he was sleeping, but calms down shortly afterwards. Peach introduces herself and Mario to Huey, but soon after they hear Toad scream and run to go help him. When they find him, his color is being drained by a Slurp Guy. Huey teaches Mario how to battle with Battle Cards and Mario squeezes Huey into paper form so that he can gain paint. After the battle, Huey tells Mario that he now has the ability to use the Paint Hammer.
Later, in Cherry Lake, Huey introduces the Cutout technique so that they can get through the gate at the beginning of the level. The technique allows Mario to use Thing cards to solve puzzles, to cut out clear lines of the background in order to traverse areas if he isn't able to continue, and to find hidden Battle Cards.
Huey teaches Mario how to use the Battle Spin after a Slurp Guy attacks them right after the Card Connoisseur Toad borrows all of Mario's Battle Cards. The Battle Spin allows Mario to get extra cards for ten coins when he runs out. Huey gives Mario enough coins to use the Battle Spin until he defeats the Slurp Guy.
At Mustard Café, Mario briefly loses Huey due to wind blowing both of them into the giant hole that the purple Big Paint Star repainted. Mario must save Huey from a Green Pokey to get him back. While the Pokey has Huey, Mario cannot use his Paint Hammer or the Cutout technique.
During the battle with Bowser, Huey turns back into his 3D form so that he can absorb the black paint that Bowser uses to attack Mario with. If Mario takes too long to defeat Bowser, Huey will be knocked out, giving Mario an instant Game Over. After rescuing Princess Peach, Huey tells Mario, Peach, and Luigi to go back to Port Prisma without him, so that he can contain the black paint and release it where it can do no more harm, turning the castle into a card in the process. When Mario achieves all of the Super Flags in Port Prisma, Huey can be seen falling back into Prisma Fountain at the end of the staff credits.
Huey is very friendly and cheerful. He has a large connection to paint, and is angered to see it get misused or wasted. He is also slightly greedy, which is shown when he sees the giant Coin in Mondo Woods, though he values friendship more than money. Huey is also shy in front of crowds, which is shown in The Emerald Circus.
Powers and abilities
Besides floating freely above the ground, Huey also is often able to smell Mini Paint Stars and Big Paint Stars from long distances. He has the ability to absorb large amounts of black paint, as seen in Sunglow Ridge and the battle with Bowser. Huey also seems to be fairly strong, as he is able to hold Mario with just his handle in Kiwano Temple, and he is also able to wring out Bowser's entire castle. Mario and Huey are also both able to hear the Big Paint Stars' voices and see their memories in their heads.