'Fallout' Cast Answer Fallout's Most Googled Questions - REACTION! 

Gulpers are mutant salamanders. Since most people don't know what salamanders are, they are an order of four-legged amphibians that go back at least 160 million years, and currently comprise about 816 species worldwide. Most go through an aquatic larval stage when they are young, though some species are entirely aquatic. Salamanders have four fingers and five toes, can regenerate, and are almost exclusively found in temperate regions of Northern hemisphere. North America in particular has greater salamander diversity than any other continent. The gulpers featured in Fallout 4's Far Harbor DLC are clearly based on the North American Hellbender and its relatives the Chinese and Japanese Giant salamanders, respectively. These aren't found in Maine, though they actually make sense West Virginia. The gulper featured in the show is clearly mutated like a Fallout centaur, and fused with something else, but it features external gills resembling those of an axolotl or other larval salamander.

Deathclaws/ behemoths/ assultrons. Do giddy up buttercups count?

Good guys? NCR are probably the closest things to good, but everybody is desperate, and goodness is a luxury if you're starving and need clean water.