Others consider the position to involve the man squatting over his reclined partner while the testicles are repeatedly raised and lowered into the mouth. Behind the Green Door was one of the first pornographic films to feature sex between a white actress with a black actor . In contrast, a celebrity may take the route of openly releasing the tape and benefit directly from royalties as well as indirectly from the publicity. Pegging films include Strap It On , Babes Balling Boys , Strap Attack, Strap-on Sirenz, Strap-on Chicks, Boss Bitches , various movies produced by LEDA Studios, and San Francisco-based Men In Pain. For a foot fetishist, points of attraction include the shape and size of the foot and toes , jewelry , treatments , state of dress , odor, and sensory interaction . These actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. Group sex also occurs in populations of non-human animals such as bonobo apes and chimpanzees. Some masturbate only using pressure applied to the clitoris without direct contact, for example by pressing the palm or ball of the hand against underwear or other clothing. Lolita pornography gay sex video caters to ephebophiles. Some people masturbate by using machines that simulate intercourse. People may also find masturbating with friends helps lift the stigma they feel surrounding the act. Cartoon pornography includes, but is not limited to, hentai and parody renditions of famous cartoons and comics. Clothed female, naked male pornography features naked men and clothed women; typically, the women humiliate and abuse the men or perform fellatio and/or handjobs on the men. Hentai narrow Japanese usage and broad international usage are often incompatible. It is geared towards heterosexual men, who most typically define a threesome as such. Perhaps following the example set by gay pornography, they have become a popular subgenre within heterosexual pornography since the turn of the century, featuring both vaginal lesbian milfs and anal ejaculations.