At the end, when the camera zooms out on Big Leo, it's the same shot of the bird's eye view of DM looking up at King Leo earlier. But you can still see DM's image looking up at King Leo.
Greenback's desendant: 'Big Leo has spoken'
The planet (or at least London) is ruled by a Greenback look-a-like who keeps his identity hidden and pretends he is a feline. He comunicates via a loud-hailer and seems to instill fear and respect in the cats. This is very reminiscent of George Orwell's book '1984'.
The title is also reminiscent of 'Planet Of The Apes'. cats being DM's chief fear as apes are to humans (the fear that they may 'evolve').