Ruby and Sapphire series
Wigglytuff's first appeared in the Kanto Grand Festival. It battled alongside Harley's Cacturne against May's Eevee and Munchlax, where Harley fully used its capability to expand its rubber-like body. Wigglytuff proved capable of moving in midair and held its own against Munchlax and Eevee. After Cacturne was defeated, Wigglytuff went to use Body Slam, and despite missing, it used its ears to throw Munchlax and Eevee away and using Double Slap on them. Eevee and Munchlax fired Shadow Ball and Solar Beam, to which Wigglytuff evaded. May had her Pokémon repeat their attacks, but only to collide and throw Wigglytuff off balance. Thus, Wigglytuff was defeated by May's Munchlax's Focus Punch, with the help of Eevee.
Diamond and Pearl series
In a flashback of May's, Harley and Wigglytuff were training for contests.