Among fetishists, the pose of reluctance—the victimization of the cuckold—is a major element of the paraphilia. The genre is popular enough in Japan gay fuck that it is even the subject of parody. Felching is a sexual practice involving the act of orally sucking semen out of the vagina or anus of one partner. The Girls Gone Wild series is one example. Today, pornographic naked milf films can be sold or rented on DVD, shown through Internet and special channels and pay-per-view on cable and satellite, and in adult theaters. A person may be sexually penetrated multiple times simultaneously. Reading or viewing pornography, sexual fantasy or other erotic stimuli may lead to a desire for sexual release such as by masturbation. The primary subjects of pornographic depictions are pornographic models, who pose for still photographs, and pornographic actors or porn stars, who perform in pornographic films. Mammary intercourse has sometimes been considered a perversion. Ass to mouth is a slang term primarily used to describe the withdrawal of a penis from the receptive partner anus followed by the immediate insertion into the receptive partner mouth. It may occur more frequently in private situations, such as spontaneous sexual activity among three friends, or arranged hentai sex in a community of like-minded swingers or planned as a once-only experience; and rarely in anonymous settings, such as at orgies or other sex parties. A 2009 study found that heterosexual male fat admirers preferred females that were clinically overweight and rated both overweight and obese women more positively than slighter individuals. In these research publications, it is suggested that real female ejaculation is the release of a very scanty, thick, and whitish fluid from the female prostate, while the squirting or gushing shown frequently in pornography is a different phenomenon, the expulsion of clear and abundant fluid, which has been shown to be a diluted fluid from the urinary bladder. Sadomasochism refers to the aspects of BDSM surrounding the exchange of physical or emotional pain.