She is mentally ill, Pauley. I believe due to her childhood she never fully developed into an adult. She laughs like a 12 year old girl. Ever see a group of 12 year old girls together? They just laugh and laugh for no reason. That's Robin. And for some reason, Howard has been able to put up with it for years. I sympathize with her due to her health problems. I hope she is able to recover from whatever ails her. However, she is truly crazy and makes it really difficult to listen to the show.