Pikachu functions as Ash Ketchum's primary Pokémon partner. During the adventure "Pikachu no Fushigina Fushigina Daibōken," Pikachu participates in leisure activities alongside trainer-owned Pokémon at a playground. While playing, Pikachu and Piplup overshoot a slide into discarded tires. An unintended collision sends the tires rolling, carrying them to an unknown area. A disoriented Unown plummets from the sky nearby. Pikachu converses with the Unown, showing concern for its situation. Team Rocket's Meowth witnesses this exchange and schemes to seize Unown for monetary gain. An Eneco appears, suggesting it guide Unown home after recognizing similar radiant energy. Pikachu, Piplup, and Unown follow Eneco underground, shadowed discreetly by Team Rocket and Brock's Croagunk. The party discovers a wall with three protruding blocks. Eneco and Pikachu activate the blocks sequentially, unleashing a dimensional portal that pulls all present Pokémon into Unown's realm. This dimension displays Tetris-like block formations. Movement proves physically demanding here, and Piplup briefly suffers spatial confusion before realigning with Pikachu. Pikachu consistently shields Unown throughout the trek. Pursued by Team Rocket across shifting dimensions, Pikachu enlarges to mega proportions relative to its adversaries. Team Rocket lands on Pikachu's head, provoking Pikachu to charge a Thunderbolt. Meowth warns this attack risks permanent paralysis. Before release, Mime Jr. executes Teeter Dance, breaking Pikachu's focus and dislodging the pursuers. Later, the lake guardians Uxie, Mesprit, and Azelf provide nourishment. Advancing, they face a tornado-like vortex of revolving blocks. Climbing becomes arduous until Deoxys intervenes, teleporting them to the summit where Unown's colony dwells. After Unown reunites with its kind, Pikachu and allies portal back to their origin point, witnessing fireworks. Pikachu possesses yellow fur, a lightning bolt-shaped tail, and red cheek pouches that store and discharge electricity. This biology permits Thunderbolt usage in conflicts. Behaviorally, Pikachu exhibits curiosity, defends vulnerable beings like Unown, and persists through perilous settings. Socially, it sustains collaborative bonds with trainer-associated Pokémon such as Piplup and Croagunk during the interdimensional expedition.