My cat seems to have better ears than I do. Whenever I'm working on a mix, she likes to climb up and lie on one of the monitors (she seems to prefer the left one).
Once in a while, something will seem to annoy her and she'll climb down. It's usually when something is out of balace or overly eq'd or proccessed.
Inevitably, once I get the mix together, she resumes her place on the speaker cabinet and stays until the end of the session (or until I break for lunch).
And no, I can't say that I've noticed my stereo image leaning to the left to compensate for any high frequency absorption that she may supply.
I don't know what I'll do if I am ever without my mixes' most insightful critic!!