Conjoined twins is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find similar stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins, as there are some monozygotic but non-conjoined twins who also share these structures "in utero". The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (1811–1874), Thai brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were labeled
Trigger Twins Secret Society of Super Villains. As part of an army, they are sent to destroy the city of Metropolis. Another army of superheroes face them. During what is called "Battle of Metropolis", the twins are shot down in the street by a group of vigilantes that include the current Vigilante and Wild Dog who were perched on a nearby rooftop. This battle takes place in "Infinite Crisis" #7. During the "Blackest Night" crossover, the Trigger Twins are among the many deceased villains that receive a black power ring, reanimating them into Black Lanterns. The Earth 18 version of Trigger Twins