What are my cats doing? One of many weird rituals?

My cats really freak out when I laugh. Something will set me off, and their interest gets peaked. Then they start crying and running toward me. If it's Rukia closest, she'll immediately try to bite me--this is the only time they bite. But my other cat and her twin, Hisana, usually runs up to her before she can do this, pins her, and bites somewhere on Rukia's neck while kneading the other cat with her back paws. This seems to calm Rukia down and send her into an almost lethargic state. If I continue to laugh or am laughing REALLY hard, both may try to bite me while crying and meowing loudly. What is going on here?