Management: the brain, it makes decisions processes information. (Hey maybe they don't make great decisions, but they make the decisions :)
Collection Development: The eyes, need to find good things to eat, books. If you can't find books that are good, you won't have a healthy body.
Reference/Outreach: the mouth, the ability to speak. If you cannot speak, people cannot gain your knowledge or find out more about you.
Circulation/Technology: The heart, keeps the body alive. Without the heart, the body would die (aka library would close).
Technical Services: The digestion system, it digests and processes the food (new books) that enters the system. Without this function, the body cannot add new books and build a healthy body, eventually making it unhealthy and ultimately killing the body.
Programming: The muscles, the body needs exercise, programming provides a variety of activities to keep the body (and mind) sharp.