Alphamegamia refers to a philia where one feels compelled to play out fantasies as an adolescent/baby. Ageplay is a form of regressive roleplay in which a physical adult takes on the role of a child. This may be purely regressive (in order to re-experience childhood in a non-sexual sense), or sexual (the roleplaying of a child/adult relationship in sex, which may be a sexual fetish and is often grouped within BDSM).

Roleplaying adult/child scenarios sexually is controversial as it can arouse concern in many people's minds, due to the sensitive nature of its subject matter. However as with other sexual fantasy it is not, by itself, necessarily a problem, and can be for some, a healthy or healing outlet, and for others like any fantasy an exploration of different roles and feelings.