Lanny (Portrayed by Vincent Schiavelli) is an alcoholic artist and freak,with an underveloped conjoined twin Leonard,who is able to detach himself from Lanny's body. Lanny knew his bother was responsible for the murders but did not turn him in when caught. Lanny mournfully suggests that the motivation behind his brother's attacks is that he is seeking a new brother, as a replacement for the alcoholic Lanny, by attempting to burrow into their side. Lanny later dies from his drinking problem, which severely damaged his liver. Scully says that his autopsy revealed many abnormalities in the arrangement of his blood system, esophagus, and other internal organs, which were almost umbilical in nature. (TXF: "Humbug")
Leonard is, in spite of his condition very strong and fast, bearing many similarities to a Tooms (an earler monster of the week). Namely the ability to squeeze threw seemingly impossible spaces and tear people apart with his bare hands. But was no match for the Conundrum, who killed him in self defence and ate the body. Though Lanny seemed to believe Leonard is seeking a new brother and claims he always hated him, it's more likely he knew his brother's drinking would soon kill Leonard and by extension Lanny. Leonard was desperate to find a new host before that happened, and if he did hate him the alcoholism likely had something to do with it.