The cat scene is, to the best of my knowledge real and that cat does get killed. What I've always found interesting is that people seem to get upset about the cat being killed by rats, but in the scene where the fire breaks out there are dozens of rats running around on fire which nobody seems too bothered about.
The film is also notorious for its use of real corpses in scenes, though this only occurs once. There's a scene of a body in a decompression chamber that is credited as real quite often, which it isn't. There is however a scene of an autopsy on you young boy which is real (I think the boy was killed i a car accident).
There's an interview with the director I read a while ago at http://www.horschamp.qc.ca/9901/offs...anBehind1.html
if anyone's interested.
I recommend his follow up film Black Sun: The Nanking Massacre. It's less of an exploitation film than MBTS though still excellent and very brutal.