You look like you came up behind a mule an' the critter did a mite of dancin' backwards!
You appear as though you were kicked in the face by a mule because your face is beat up. 
mnli hypothesis: You appear as though you were kicked in the face by a mule because your face is beat up.  premise: You look like you came up behind a mule an' the critter did a mite of dancin' backwards!