"The unicorns, though, they tend to have more along the lines of artistic, mystical or scientific types of marks. Stars, for example, or paintbrushes. I saw one with an hourglass, even! The winged ponies tend to have ones based on weather, such as clouds, rainbows, that kind of thing. There is some crossing back and forth, such as the unicorn we saw earlier with the clover mark, but our best guess is that it is some kind of caste system, with the plain ponies most likely on the bottom, though there doesn't seem to be any real social separation between the classes." 