Any person with Zerophilia
, the rare genetic condition affecting those who possess an extra "Z" chromosome in addition to the standard gender-determining X and Y chromosomes. Following their first experience of sexual intercourse, Zerophiliacs may change gender whenever they are sexually aroused. The International Organization of Zerophiliacs provides testing services and resources for those with Zerophilia
When she noticed her boyfriend, Jake's, penis occasionally disappeared, Mary submitted his hair for testing to The International Organization of Zerophiliacs and confirmed her hopes: Jake is a Zerophiliac.