I'm with mollie on this one. It's a simple case of the wonder putting her wants and needs before the cats. As pet owners we have a responsibility to ensure the highest standards of welfare for our pets, sometimes that means euthanasia. The cat is unbalanced, he falls or wobbles several times in the video, he will be completely unable to complete natural behaviours such as play, hunting, climbing, and will have to put a massive physical strain on his body. When a body is stressed, it releases cortisol which has massive negative affects on various systems, the immune system is dampend, chronic pain is more likely, phantom limb pain is common for amputees (and there is suggestion that animals get it too), the liver is in overdrive trying to produce glucose for energy, which means digestion is affected. The list goes on.
One limb missing witll put stress on a felines body, but not unmanageable stress. Two limbs however, cannot be ethically sound, it compremises his welfare, and that's not acceptable.