This otherwise plain sorrel horse with very unusual white markings on his hindquarters recently visited one of the barns where I teach, causing people to speculate whether he was a Paint with spots inside spots or an Appaloosa whose blanket didn’t quite form.
According to the owner, who had clearly (cheerfully) answered the question before, neither. He’s a crop-out Quarter Horse. (Named Bulls-eye!)
Of course I knew sometimes Quarter Horses produced a little too much white, though rules have been relaxed so horses that used to be ineligible for QH registry are now welcomed. But in digging around for information on crop-outs, I learned that there also have been instances of Quarter Horses producing Appaloosa coloring.