The guardian of Prisma Fountain in Paper Mario: Color Splash is Huey.
Huey initially appears as a paint can hidden in a vault beneath the dry fountain on Prism Island. When Mario tries to open the can, it reveals itself as Huey, the fountain’s guardian. He explains that the fountain’s six Big Paint Stars provide the island with its seemingly endless supply of paint and color.
Mario joins Huey on a journey across Prism Island to recover the missing Big Paint Stars. Their search leads through six areas and eventually reveals that Bowser accidentally created toxic black paint while trying to recolor his shell. The black paint possessed him and drained color from the island.
Huey remains important through the ending. After Mario defeats Black Bowser, Huey absorbs the dangerous black paint and the collapsing castle, then flies into space to protect Prism Island. The post-credits scene can show him returning to Prisma Fountain, depending on the player’s progress.
The main mix-up is with Kersti, the sticker fairy from Sticker Star. Huey belongs to Color Splash and is visually represented by a paint bucket.