Snorlax is the Pokémon called Mosslax after sleeping so long that moss and other plants grew over it in Pokémon Pokopia.
Mosslax is a story-specific version of Snorlax whose defining feature is an exceptionally long sleep. The plants covering its body reflect the game’s abandoned-world setting, where natural growth has continued without human maintenance and Pokémon have adapted to unusual conditions.
The nickname can be confused with Munchlax, Snorlax’s pre-evolution, because both Pokémon are strongly associated with eating and sleeping. Mosslax, however, is explicitly based on Snorlax. Slaking and Komala also sleep frequently in the Pokémon series, but neither is the character described by this Pokopia name.