Pinpuku, known as Happiny in English, appears as Brock's Pokémon during the film. It travels with Brock as part of Ash's group visiting Alamos Town.

Pinpuku acts protectively toward Brock. When Brock flirts with the hot air balloon tour guide, Alice, shortly after arrival, Pinpuku interrupts him using Poison Jab, a recurring action managing Brock's romantic advances.

As part of Brock's team, Pinpuku participates in routine activities but does not engage in the primary conflict involving Dialga, Palkia, and Darkrai. Its presence is noted during group interactions, such as when Brock releases his Pokémon to play in a garden alongside Ash and Dawn's Pokémon. A minor disturbance occurs among the gathered Pokémon during this scene, though Pinpuku remains uninvolved in the ensuing chaos.

Pinpuku's biological characteristics align with its species. It carefully carries a small, round, white stone in the pouch on its stomach, mimicking Chansey's egg, which it believes to be real. The species lends this stone to those it trusts but becomes upset if the stone is not returned. Pinpuku also exhibits self-consciousness regarding the curly appearance of its hair. Its behavior includes wandering near others' feet, which can cause stumbling.