Why would a 1996 Pontiac Sunfire's engine be making a hissing or metalic rubbing like noise at all engine speeds?
Flex plate (you might know it as the fly wheel) rubbing on something? Bad alternator? Trace the sound to where it's coming from, describe and ask again.
It's the smell of the vet's clinic. You could: A) Seperate the cats for a couple days until the smell wears off or B) Give the kitty a bath. I've also seen a suggestion to rub a towel into the hissing cat's fur and then rubbing it on the one that went to the vet, but I haven't tried it myself and it sounds like it might only help a little.