So first of all, werewolves aren't real. Let's get that out there before we get too ahead of ourselves. People often refer to hypertrichosis as the "werewolf syndrome" because it causes excessive and abnormal hair growth, and we're not just talking luxurious locks down your back. Hypertrichosis can cause hair growth pretty much any and everywhere. As it turns out, hypertrichosis might actually be a genetic condition where extra DNA causes a hair-growth gene (possibly SOX3, for those playing gene bingo at home) to go nuts [source: Live Science].
Of course, hypertrichosis was also the reason that famous performers like Jo-Jo the Dog-Faced Boy were presented to the public as half-beast [source: Pednaud]. At times Jo-Jo acted the part and humored audience members by growling at them. More recently, Percilla Lauther was a famous sideshow performer who lived with hypertrichosis that manifested on her face and body. She happily worked with her husband (another sideshow performer) until late in life and died in 2001.