Each two-headed worm creature has two heads, two arms, three legs and "two asses". Each head has his own individual personality. In most cases, the right head is the dominant one, treating the other like a slave and sometimes even being sadistically evil to or even pimping out the left half. However, it is not impossible to find a two-headed worm creature where both heads treat each other like equals. The best known example is Martin who is a regular student at Mark Lilly's class in the Department of Integration.
All two-headed worm creatures are direct descendants of the original worm creature whose name was Mitch.
They can be surgically separated, but at least one of them is going to have major health issues. The healthy one will eventually give birth to a new baby head, which may be derived from the earth worm's regeneration.