Mental Affair: Fairly common, or at least the “virtual reality” kind is; species generally don’t come equipped with the necessary hardware to do this sort of thing naturally. Popular for a variety of reasons, including obviating distance, permitting all kinds of things from, well, extra stamina to Power Perversion Potential that the material world has, ah, trouble with, and – for those having sex outside their species – making Boldly Coming work for couples who don’t share the same atmospheric composition, pressure, and temperature requirements, or have other similarly extreme physical incompatibilities.