Michael John Berryman (born September 4, 1948) is an American character actor. Berryman was born with hypohidrotic ectodermal dysplasia, a rare condition characterized by the absence of sweat glands, hair, and fingernails; his unusual physical appearance has allowed Berryman to make a career out of portraying characters in a number of cult films, horror films and B movies. He first came to prominence for his roles in Miloš Forman's One Flew Over the Cuckoo's Nest (1975) and Wes Craven's The Hills Have Eyes (1977). He has appeared in a wide range of feature films and television series, including Star Trek, The X-Files, and Highway to Heaven, in which he portrayed Satan.