Some do not use the diapers at all, for arousal, or bladder and bowel movements. 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. This hentai videos style of filming is in contrast to having a separate, third-person camera horny milfs crew filming all the action. Others involve partners who naturally have a significant difference in size. Facial cum shots are currently regularly portrayed in pornographic films and videos, often as a way to close a scene. The exact source and nature of the fluid continue to be a topic of debate among medical professionals, which is also related to doubts over the existence of the G-Spot. Pornographic films present sexual fantasies and usually include erotically stimulating material such as nudity. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. Fantasies of group sex are extremely common among both men and women, and group sex is a subgenre in pornographic films. For other scenes, particularly in established relationships, a safeword may be agreed to signify a warning rather than explicit withdrawal of consent; and a few choose not to use a safeword at all. Babysitter pornography features usually teenage girls being exploited and having taboo sex with older, male employers. Teacher and Student or Boss and Secretary pornography involves sexualized young gay porn situations which take place between an authority figure, such as a teacher or boss, and an underling, such as a student or secretary, often fake. Can also include auto-fellatio, or performing oral sex on oneself. Unlike erotic films, pornographic films contain explicit sexuality and do not claim any artistic merit. It may involve sexual attraction to women who are pregnant or appear pregnant, attraction to lactation, or attraction to particular stages of pregnancy such as impregnation or childbirth.