One or more of the participants may engage in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. Pegging is a sexual practice in which a woman performs anal sex on a man by penetrating the man anus with a strap-on dildo. Interracial pornographic films have experienced an explosion in popularity, becoming one of the fastest-growing and biggest-selling genres. Some productions are noted for sophisticated and/or experimental storytelling and animation techniques. High heel pornography involves women or men dressed in high heeled shoes. Real enema shots or videos of true medical situations may violate privacy laws in some countries. Pornography in the early 2000s. Other possibilities gay twinks are possible, such as a man having sex with two women who are having sex with each other. Fisting involves the insertion of one partner entire hand into a vagina or the anal cavity. A variant of this lesbian hentai is known as ATOM or ATOGM where the insertive partner removes his penis from one recipient anus and inserts it into a second recipient mouth. Foot fetishism, foot partialism, foot worship, or podophilia is a pronounced sexual interest in feet. Bukkake, Gokkun, Omorashi, and tentacle erotica are few uniquely Japanese genres known to western viewers. Pornography is generally classified as either momsex softcore or hardcore pornography. However the genre remains a very small proportion of the pornographic DVD market; for example at porn retailer HotMovies. But starting with The World Biggest Gangbang , starring Annabel Chong, the pornographic industry began producing a series of films ostensibly setting gangbang records for most consecutive sex acts by one person in a short period. Some restrict a policy of panties/nipple tape for females and some allow full nudity with explicit sexual interaction allowed. The term soft crush refers to the more common fetish surrounding videos involving inanimate objects or small invertebrates being crushed, while the term hard crush refers to such videos involving larger animals with vertabrae, and arguably more pain-susceptible animals .