How do you get Munchlax in Pokemon FireRed?
Munchlax is a 4th generation Pokemon meaning it only exist in diamond and pearl and platinum and heartgold and soulsilver so that means munchlax is not a Pokemon you can get in firered. Though in Pokemon xd gale of darkness you can witness munchlax even though you can't get it you can see it and also you can see and use bonsly in the game.
First off, Munchlax is a 4th Generation Pokemon and is thus not available in Pokemon FireRed or LeafGreen. Make sure you are playing Pokemon Diamond, Pearl, Platinum, HeartGold, or SoulSilver. The Snorlax must then be holding a Full Incense in the Day Care in order to produce a Munchlax egg. Full Incense can be found in Veilstone City (in D/P).
Munchlax can be caught from honey trees. Slather honey on some trees, wait six and a half hours, and check back to see if there is a Pokemon. If Munchlax isn't there, just keep trying, and if that doesn't work, try slathering different trees. Another way is to migrate a male and female Snorlax from Ruby, Sapphire, Emerald, FireRed, or LeafGreen. Optionally, you can substitute a Ditto for one of the Snorlax. Let the female…
Munchlax cannot be recruited in Pokemon Mystery Dungeon. Its appearance in Pokemon Square is simply for you to gain a new item and possibly for you to get a taste of the new generation of Pokemon. Pokemon Mystery Dungeon Red and Blue Rescue Team only recruit Pokemon up until the third generation - Munchlax being from the fourth.