About cat seeing themselves in mirrors, we have to understand that only a few species in the animal kingdom has mirror self-recognition (MSR), including great apes, elephants, dolphins and some birds. There are tests to determine if an animal (or species) can recognize that the image in the mirror is in fact, themselves, and there are a few stages to evaluate that, including social responses, physical inspection (ie looking behind the mirror), repetition testing mirror behavior, and finally realization that it is themselves in the mirror. There is a very interesting book called Dolphins In The Mirror which describes the cognitive behavior and MSR in dolphins that might help you understand more about the concept.
Cats does not have MSR, I believe their reaction of seeing the image in the mirror depends on their social personality. For example, a skittish cat might get spooked, and a fractious and solitary cat would get angry, hissed or attach the image in the mirror while more socialized individual might try to 'make friend' or ignore the image in the mirror.