Sexual Chemistry is a 1999 soft-core porn/Sex Comedy film about a chemist, Robert, who attempts to create a sex-enhancing drug. There is a competition within the company where he works, with the winner becoming the new head of department, and in his desperation for results, Robert uses something his former girlfriend, Zelda (who happens to be a witch), whipped up in college. The formula has the unintended side-effect of causing him to turn into a woman, who takes the name "Heidi"; once he's take the formula once, he transforms back and forth, usually at the worst possible times. He eventually realises that sexual excitement is the trigger, and must deal with that, and with unscrupulous competitors and suspicions of his alter-ego being a spy, all while trying to stabilize his own sex.
This is typical soft-core pornography of the period, similar to that shown late-night on premium cable channels. Sex scenes are alternated with plot.
Sexual Chemistry provides examples of:
- All Women Are Lustful: Pretty much all the female characters want to have sex. Admittedly, the same is true of most of the men, while the women are capable of intelligent thought, but at one point, a female character specifically notes that there's no point in trying to make women want sex, because they already do — they just want good sex.
- Ambiguously Bi: In a film where every character of either sex appears to be straight, and sometimes makes a point of saying so, the same initially seems to be true of Zelda. However, she's openly admiring of "Heidi's" good looks, flirts with her briefly (albeit to make her excited and thus trigger her transformation back to Robert), and eventually has sex with Robert despite knowing that he might change sex at any moment. If she's not actually bi, she's a lot more relaxed about sexual ambiguity than the other characters.
- Applied Phlebotinum: The drug is developed as an aphrodisiac, but has the side-effect of transforming the user into the opposite sex.
- Casanova Wannabe: Robert's best friend, Max, fits this trope (complete with a Porn Stache). At one point he complains that All Women Are Prudes, and is promptly told by a woman that this isn't true; he just fails to appeal to them. Eventually, he does get to have sex — with the uncontrollably horny "Heidi", not knowing that this is the sex-changed Robert.
- Chemistry Can Do Anything: This drug not only transform the user into the opposite sex, it makes them younger, grows their hair and nails (and massive breasts), and epilates their body. It also seems to apply makeup. Given that the formula involved input from Zelda, who's specifically stated to be a witch, the writers evidently had to admit that this looked more like magic than science.
- Cool Old Lady: Robert's mother initially seems to be a bit of a nuisance, with some issues about being abandoned by her husband. However, she is generally tolerant of Robert's odd behavior, has a better idea of his romantic needs than he does himself, and eventually gets over her issues.
- Gender Bender: Robert takes a formula which cause him to switch back and forth between himself and "Heidi".
- Fantastic Drug: See Chemistry Can Do Anything, above.
- Jekyll & Hyde: Our hero doctor is trying to develop a drug to increase libido, and gets more than he bargained for. This differs from the usual Jekyll & Hyde plot in that his new alter ego isn't evil — just horny.
- Light Girl, Dark Boy: The brown-haired Robert transforms into the blonde "Heidi".
- Sex Comedy: While the movie is definitely soft-core porn, it includes a fair number of jokes; the situation is pretty ridiculous, after all.
