Cats manage to learn a lot of things about their environment just by the smell. Their sense of smell is way better than ours. Knowing this, it doesn’t come as a surprise that in the video after the cat farts, her sniffing buddy looks like he is in complete shock.
We must admit that Big Daddy was asking for it, when he had his nose sniffing his friend’s rear end.
One thing to have in mind is that cats have a very special sensory organ called the Jacobson’s organ. When cats make a face, such as the one the cat does in this video, it is usually so they can get the air into the Jacobson’s organ in order to get a good sniff of the smell. This is called the flehmen response and it doesn’t always mean that the cat smells something unpleasant. It can also mean that the cat is really intrigued.