Dr. Hogback is a world famous doctor, who according to Chopper saved as many people as there are stars in the sky. One day he disappeared from the public eye, causing turmoil in the medical community. Nami, Usopp, and Chopper meet him on Thriller Bark, and he explains to them that he is researching the nature of life and death using the zombies on the island. Like many other characters in One Piece, Hogback has a unique laugh (fosfosfosfos). Many members of Thriller Bark seem to be based on old Horror movie character types; Hogback seems to be based on mad scientists, in particular Dr. Frankenstein. (Source: Wikipedia)