The fact that you had just binged on carbs on a previously VLC diet suggests that the smell is of bacterial origin. I'd be willing to bet it is only a short term effect of a rapidly altered gut flora.
If you feel the need to binge, you should realize that VLC is probably not comfortably sustainable in the long-term. I would strongly recommend incorporating some sugars into your diet.
Starting 5 months ago my urine has started having an odor to it, and also is a little darker than before. What's interesting is that I'm able to tell what I ate previously by the odor of my urine, i.e. if I had beef, it smells a little beefy, pumpkins give it a little pumpkin odor. When you say cat pee, what does it really smell like, protein? beef? a certain vegetable? potatoes?
Kind of strange, but I just live with it.