The Cat, the Rat and Lovell our Dog,
Rule all England under a Hog

The Cat was Sir Thomas Catesby. The Rat was Sir William Ratcliffe of Ordsall Hall. The Dog was Thomas, Lord Lovell ( Lovell's emblem was a talbot, a now-extinct breed of hunting hound). The Hog was Richard III ( his emblem was a white boar). The couplet refers to the fact that this hated trio of men enjoyed enormous power and influence in the reign of the equally disliked King Richard III.