The saying Chill the beans has become out-dated in today's society and is dismissed as something a five year old would say. Therefore, I have upgraded to a phrase from which you tend to receive more of a reactiion from and are thus, fully understood. Chill the beanie Os is simply a phrase used to ask a person who is hyper, hypertensive, over-reacting or just plain angry; to calm down.
Your on facebook with your friends, talking about the rave you were able to get into with them last night. You then mention the girl/guy your friend decided to extract a quickee from; but in the process got slapped in the face and a beverage poured over their head. He/she completely over-reacts and snaps at you with a form of low blow. You feel your friends pain and decide to respond with a more gentle phrase, hence, Chill the Beanie O's comes into play and your friend laugh at the original phrase and forgives you.