The basis for this film is that Cal's wife, Emily, slept with another man and now wants a divorce.
The sexual content of this film is made up more in dialogue and implied instances than actual scenes. One-liners, double entendres, and crude humor fill the script. Male genitalia is referred to, Cal constantly talks about how his wife is "screwing" another man, and other references to pole dancing, oral sex (one joke talks about doing it for 45 minutes), and porno videos are made.
Cal hooks up with 9 different women after his divorce, although we only see one of the affairs, the one between him and Kate. We see them passionately kiss, caress, and writhe around Cal's apartment (in the dark), realistically, yet somewhat comically. Kate pushes Cal onto a sofa and stands on a table, shaking her backside and spreading her legs before she jumps on him and the scene cuts. No nudity.
In fact, Jacob can't believe that before he meets these women, Cal had only ever had sex with Emily. We then see both Cal and Jacob hitting on different women at the bar. As Jacob tries to improve Cal's look, we see them at a sauna, where a nude Jacob stands talking to Cal (his head covers Jacob's crotch). When Cal faints because of the heat, his head rests on Jacob's crotch.
Jacob, although it's implied he's been with many different women, is only seen in a sexual context with Hannah, who in the meantime is trying to convince herself she's "R-rated sexy." Although Jacob and Hannah plan to have sex, it's implied they don't, at least on the first night they're together. We see them kissing and caressing passionately in bed, Jacob shirtless and Hannah in low-cut underwear of sorts, but the conversations they have keep them talking all night, instead of actually going all the way.
It's obviously implied that Robbie is masturbating when Jessica walks in on him unannounced (we don't see anything except Jessica's expression and the conversations that follow). Robbie, with a huge crush on Jessica, says that he has a picture of her he does it with, and also tells everyone at a graduation speech his habit .
Jessica, interested in Cal, asks a friend who sleeps with older men what she should do. The friend, making orgasmic looks and sounds, tells Jessica to take nude pictures of herself. We see her bare shoulders and legs as she does so, but when a giant fiasco occurs with her parents finding out and assaulting Cal, the pictures end up in Robbie's hands, as Jessica kisses him on the cheek.