May's Munchlax was the first Generation IV Pokemon to appear in the Anime. It was a greedy creature, as were most of its species, and while travelling with May in Hoenn it did little except eat. It wasn't until May travelled to Kanto that Munchlax truly became part of her team. During a battle with a Vileplume, Munchlax learned Focus Punch, followed almost immediately by SolarBeam, mastering both attacks within moments allowing it to defeat Vileplume. It's first contest battle was against Harley's Octillery. Although it put up a good fight, Octillery won, making Munchlax the only known one of May's Pokemon that had been defeated by one of Harley's Pokemon. Munchlax battled Harley again in the Grand Festival alongside May's Eevee where they worked together to defeat Harley's Cacturne and Wigglytuff. Munchlax also fought alongside Combusken against Soledad but they were both defeated.
Munchlax also appeared when May travelled to Sinnoh to enter in the Wallace Cup.
It is set to reappear in the Pikachu short airing along with the 15th Pokemon movie.