Our moon is a pretty big object. It's big enough to be a respectable planet in its own right, if it were orbiting the sun instead of the Earth. (Actually, it is orbiting the sun in a nearly perfectly circular orbit, that the Earth only slightly perturbs... but that's a topic for another day.) The Moon is a quarter the diameter of the Earth. Only Pluto has a satellite that is larger, in proportion to the size of the planet it orbits.
When the city is in need, these superhero cats will do everything they can to help (i.e. look on indifferently then passive-aggressively poop on the bed).