Chang and Eng, the two young men who would eventually be known around the world as the 'original' Siamese twins, arrived in the West in 1829. They were brought to the West to be examined by medical men and to be exhibited to the general public. Throughout the 19th century in Britain and the US, 'monstrosities' such as Chang and Eng, as well as a host of other people with unusual anatomies, were considered both spectacles worthy of public display and edifying medical subjects with the potential to build on medical knowledge. The unique case of Chang and Eng illustrates that the boundary between what is of legitimate medical interest and what is considered merely spectacle is often blurred.