Hoenn
May caught Munchlax in the episode Berry, Berry Interesting. This wild Pokémon was in trouble when it was framed for stealing and eating other trainers Pokéblocks, May decided to take the responsibility for its acts, plus it was the only Pokémon May could find that liked her custom Pokéblocks, May's Purple Surprise, so she decided to catch it. But its dodging skills were too much trouble for Combusken. After it was proved innocent and became distracted eating the incoming Pokéblocks, May threw a Poké Ball at it but Munchlax ate the Poké Ball. It then activated from inside Munchlax, and it was caught.
Munchlax seemed to take a liking to Max, spending a lot of time with him. Munchlax was also the only one of May's Pokémon that was not used in her first Grand Festival. During the festival when Skitty used Assist to show off all the moves of May's team, one of the moves it used was a SolarBeam, hinting it may have been Munchlax's to her traveling partners, which proved true.
Kanto Battle Frontier
Munchlax was one of the Pokémon May took with her when she traveled through the Kanto region. In A Real Cleffa Hanger, Munchlax was shown to know Metronome. In On Cloud Arcanine, after using it to use ExtremeSpeed, Munchlax quickly ate the Pecha Berries on the trees instead of attacking the Arcanine it was supposed to. In May's Egg-Cellent Adventure, Munchlax took part in its first battle against Nicolette's Vileplume, where it was revealed to know Focus Punch and SolarBeam.
May entered Munchlax in a Contest in Harley Rides Again. It made it to the final round where it was up against Harley's Octillery. It put up a good fight before it eventually lost.
Sinnoh
Munchlax continued traveling with May when she left to compete in the contests in Johto, and stayed with her when she returned to participate the Wallace Cup in A Full Course Tag Battle!. May called it out to look for the stolen food along with Kylie's Munchlax, due to its powerful ability to sense food. Nonetheless, Munchlax was delighted to see Pikachu once again. Within a few minutes later then, it successfully located the stolen refrigerator and lead the gang to it, unlike the other Munchlax. Because of this, Kylie was highly impressed at May by how well-trained her Munchlax is.
