This was a fun image to look at. It made me think of what a two headed cat would be like in an obscure science fiction novel. The idea was really awesome in my opinion.
The focus seems a bit off, especially on the mirror side which is hard enough to get in focus anyway. I think maybe you might have set the autofocus on the mirror side or right in the middle and then moved the camera. It also appears like you used flash, which made the white parts pretty bright.
The other main problem is that the background is pretty distracting, especially that it isn't symmetrical and takes away from the symmetry of the entire image which was almost dead on. This of course would be easy to change with spot editing and its a shame you can't do it for the challenges. I'd go back and do it for my own personal portfolio if I were you, maybe just cut out the background and make it all pure black.
Oh, the whiskers are a great touch and I laughed out loud reading your photographer's comments picturing you trying to get the cat to stay on the mirror.
Great idea. A bit flat with the lighting and a little too much stuff going on in the background. The reflection is suprisingly a little blurred too. Real close to being a very good image.