This article is from the the official alt.spleen FAQ, by Andrew Stellman with numerous contributions by others.
Andrew says: NOTE: PLEASE DO NOT SEND ANY MAIL TO ME REQUESTING MEDICAL ADVICE! I AM NOT A DOCTOR, AND WILL NOT GIVE YOU ANY USEFUL INFORMATION.
Clearly, Lisa has more spleens than anyone else. All of her major body organs are spleens. All of her minor body organs are spleens. It has been postulated that the number of spleens in Lisa's body is proportional to her greatness and wonderfulness, so that number has to be pretty big. It has been rumored that Geoff replaced all of Lisa's body parts with spleens, but he has yet to confirm or deny the rumor.