23rd Oct: It's time for the second TV Tropes Halloween Avatar Contest, theme: cute monsters! Details and voting here.
"Thank god for virgin 13-year old females writing gay porn."You would expect the people creating erotica to know how sex works, and yet, the movies often depict things that wouldn't really be enjoyable, should be done differently or are just plain weird. This is usually done on purpose, to conform to what the audience wants to be true. Some of these are perfectly Acceptable Breaks from Reality, since such works caters to customers' sexual fantasies rather than reality and is intended to provide an arousing display of the participants rather than a strictly accurate depiction of the act. In other words, Reality Is Unrealistic. However, this also shows up in a lot of Fan Fic because said fiction tends to be written by teenagers who don't know all that much about sex. It can also be an effect of lack of research before writing about anatomy that the author lacks. Better to just use a Sexy Discretion Shot and call it a day. Sadly, this trope sometimes pops up in works and speeches not clearly labelled as fiction: In Real Life, sex education fails YOU. The average high school sex ed course in many countries, especially the United States, is often so hilariously incomplete and inaccurate that it leaves you completely unsurprised that most students walk away knowing very little. Compare with Idealized Sex, where the sex is realistic in action but still more idealized than most sex in the real world. See Miss Conception, Technical Virgin, and But We Used a Condom for when characters are mis- or uninformed about sex facts.
— America, Axis Powers Hetalia, "Buttsex: The Musical"
Common versions (no specific examples needed):The common versions can be divided into three broad categories: exaggerations of reality, convenience tools, and completely impossible.
ConvenienceThese remove inconvenient bits of reality. Certain needs that actual sex would require, but would affect the pacing of the sex/story.
ExaggerationsThese are at least theoretically possible, but for them to happen in reality would require nigh-superhuman sexual capabilities and/or stamina. Also covers cases where they are very possible, but the frequency of their occurrence in the wild is exaggerated.
Plain impossibleThese are not physically or anatomically possible by any stretch. They represent imaginative fetishes at best, or just severe cases of not knowing how human bodies work at the worst.