Mistaken identity does not just affect identical twins, it can also affect the lives of unrelated individuals. The present article reviews several compelling cases in which confusion by others significantly altered the life circumstances of twins and non-twins. Next, current research on ovarian transplants, kidney donation, false beliefs and emotion understanding are reviewed. The concluding sections survey some unusual twin pairs — and pay tribute to the late Dr. Daniel G. Freedman, known for his landmark studies of fear of strangers in infant twins.