My father's surname is a fairly rare one, and the vast majority of American McFatters/McPhatters can be organized into more-or-less coherent family trees. Sure, once you get to pre-Revolutionary times, it's hard to suss out exactly how everyone's related, but after that, things get a lot clearer.
There's a handful of "strays" who were frolicking around with this surname who, for the life of me, I CANNOT identify how they're related. Here are the most confounding cases:
John Leslie McFatter, born about 1877. Census records indicate he was born in Mississippi, but he does not fit either into my father's branch (Claiborne county) or the Carroll-Montgomery-Webster-Attala branch. He enlisted in the army in 1904 in Kansas City, Missouri, so I wonder if he wasn't born in Missouri (sometimes abbreviated "Miss" on records, thus confusing it with Mississippi). He lived most of his adult life in New York and Virginia: https://www.wikitree.com/wiki/McFatter-65
Austin McFatter is quite confounding. He first appears in 1860 Jackson co., Florida living with a family of Pittmans. There was a known branch of North Carolina McPhatters who had moved to the Gadsden county area before Austin's birth, but none of them had a son by that name. BUT!! There is a child of the right age in the 1850 Gadsden co. FL census, living with parents Archibald and Sarah McPhatter... but that child is named Christopher. Is Austin the same person as Christopher? If not, who IS he? Weirdly, Archibald and Sarah McPhatter had another son named John in 1850, who vanishes after that census, but a "Arch" McFatter of the right age appears in 1860 living in Gadsden co. FL with the family of Green and Frances Arnold. Are "Arch" and John the same person? What in the world is going on? https://www.wikitree.com/wiki/McFatter-37