I've never seen this before, but on a trip back from BLQ recently a gentleman had his cat in a cage and brought it onboard as cabin luggage. We went through security at the same time, and he had to take the cat out of the cage, and walk through the scanner with said feline draped around his neck with no lead or harness.

I was a little curious as to this procedure , as some cats may have taken the opportunity to make a bid for freedom, possibly airside. This particular cat was as good as gold in this case, but is this standard practice?