As described by Gordon and Mr. Blik: there be no mouse more mean, and ugly, and clever, and ugly, and perilously, dangerously, undeniably UGLY as Squeakus the Mouse. Of all the mice in the world, he is the uncatchable one, he's flung to the ground more cats than you can count on your paws.
On his first appearance, he had tricked Waffle into believing he's not a mouse. Not only that, he had further tricked Waffle into believing his own BROTHERS were mice. He was later finally taken down by Waffle's cat breath attack. He is last seen greatly injured, squatting in one of the Cramdilly Mansion’s air vents.
On his second fib to him, Squeakus had told him Blik and Gordon were mice. The two don't look at all like old women (as he had Waffle believe before) so it's odd how Waffle didn't see through his lies.