"Moemon" (short for "Moekko Monsters") is a prominent hack of Pokémon FireRed and Emerald that changes all Pokémon into gijinka. It is a simple change of the third generation games, however, some small changes other than the sprites are prominent such as the ability to catch the three starters, Eevee, and a mix of both LeafGreen and FireRed Pokémon (thus making it simpler to obtain all Pokémon). After the success and attention of FireRed the hacker released a modified version of Emerald, like the original modifications in FireRed a few aesthetic changes have been applied in Emerald, for example, to both Route 101 and Littleroot Town, adding many puddles to the town, and the Oran Berry has, curiously, been renamed the "Weed Berry", possibly for comedic effect.
The game still receives a fair amount of attention, as a patch was released solely for the FireRed hack that updated both the sprites of the Pokémon as well as their menu sprites, functioning like DLC would for any game.