The player controls Cryptosporidium 137 , a member of the Furon race of aliens , who has come to Earth to harvest DNA from humans to continue the cloning process of his species . The player controls Cryptosporidium 137 ( a reference to the protozoan parasite Cryptosporidium ) , a member of the Furon race of aliens , who has come to Earth to harvest DNA from humans to continue the cloning process of his species .