Toby Bartels says: I like the anthropology (if I can use that word) here, explaining when animals go naked: when they're children (or Sheldon's father, which tells you something about him). I'd expect that nakedness is also more common in rural areas; Chloe lives in the sticks, but Michelle may live here in town. This is like wearing shoes in America a hundered years ago ... or nakedness in tropical regions (at least before whites took over).