And the bonus answer is.....
(Good job "the mad woman behind the blog"! I will have to pick a harder question for you next time!)
You might be surprised to find out it's the skin, because you might not think of it as an organ, but IT IS!
Skin is composed of water, protein, minerals, chemicals, and lipids and serves a variety of functions for the body. The average weight of the entire organ is about six pounds, and skin helps to protect the body from germs and infections. Skin is constantly changing and regenerates itself about every 27 days!