I think the idea is not so much that the UV light is reflecting off them and lighting them up (like a black light does, particularly to white objects) but that the fluorescent whatchamacallit is actually causing them to generate a glow of some kind when exposed to the UV light.
Lots of stuff glows in ultraviolet. Make a cat that I can see glow and I'll be impressed.
Regardless it's kinda freaky-lookin =P
Also, glow-in-the-dark cats. Cool.