"Pip and Flip- Twins from the Yucatan" were actually Jenny Lee and Elvira Snow from Georgia.
They suffered from microcephaly, characterised by abnormally small craniums which gave rise at the time to the term “pinhead”. Like most microcephaly sufferers the Snow sisters were mentally retarded, but although based at Coney Island, they also travelled with the World Circus Sideshow for many years.
You might recognize them in Tod Browning’s 1932 film “Freaks”. (x)