I bred a male Snorlax and Ditto, and I was meaning to get a Munchlax. But when the egg hatched it was just another Snorlax! How did this happen and how do you get a Munchlax by breeding?!
In order to Hatch a Munchlax, you must give your Snorlax a Full Incense and Breed it again.
Source : Personal Experience
Full Incense. Give your Snorlax a Full Incense and breed it. The baby will be a Munchlax.