It seems to be a universal thing with cats, every cat that has lived with me does this. Some cats just chirp, while others really get into it with a meow along with the cackling, and they hold their mouth open, then shut it like it is a nervous tick or something. I love my cats, just 2 nights ago my tiger cat Angel and I were watching TV, when Angel's attention was distracted to something crawling across the floor toward me. It was a 5 inch CENTIPEDE!! If Angel had not have seen this bug, I might have been stung. Can you imagine one of these beasts getting in bed with you?Last year that happened, another centipede, but smaller, was caught by my bed lounging cat. Well, I'm glad both my cats share my bed(like I have a choice). Thanks for the replies, I hope my centipede story didn't scare you, but it is a true story..:>)