Everyone is posting their Lore Takes on the ghastlings and I wanted to throw my hat in the ring
I don’t think this addition implies ghasts are native to the overworld or are inherently amphibian becsuse they have gills. At all.
Rather, I think the ghast is a nether creature and some just dont make it to adulthood. Some just don’t get the necessary resources to stay alive and grow up and they dry out. Maybe it’s because the soul sand valleys ARE so dry compared to the other nether biomes and that’s why they spawn around the fossils that only spawn in the valleys. I think some ghasts just dont make it.
I think the ghastling and the happy ghast are Happy in the overworld and regular ghasts are sad not becsuse they’re native to the overworld but becsuse You Saved Them. From. Death. I think hell is a difficult place to live, but be it coincidence or not in lore, in game design they’re obviously supposed to represent ghosts in a way, and I think they frown and cry for another reason. Maybe because they’re corporal ghosts, maybe another reason. I don’t know. But I think the happy ghast is happy because it was saved, not because the ghast species comes from the overworld.
To the water, I do think they gain the gills because they are revived in water. I don’t think they’re inherently amphibious or aquatic becsuse regular ghasts don’t have gills. I think we the player can’t revive the ghast using its normal growing process and so we do what we can with the tools we CAN use - water - and in this the ghast sort of evolves to account for it. And of course the reason the ghasts eat snowballs is becsuse it’s another method of cooling, keeping them moist and not drying out, and acclimating them to the overworld.
I dont think every species in minecraft that isn’t a real world animal needs a deep lore history of “it was in the overworld but banished to the nether” or anything crazy. I think the ghasts are nether creatures but in the process of being revived in the overworld gain the gills to survive the water.
ADDITION - now that I think about it the fact minecraft dungeons HAS baby ghasts could tie into the fact baby ghasts do exist and some survive and grow into regular ghasts. I know Dungeons is dubiously to not canon but I like taking it into consideration and the fact we have a different Version or Species of baby ghast in that game makes me think they probably do grow up normally, but some unlucky babies dry out in the soul sand valleys and basically die without player intervention.
