The genre of babysitting is one of the most specific in the realm of film. The formula is even more generic than that of the romantic comedy--the only difference being that babysitting movies are far less vomit-inducing. And, by the end, the babysitter is typically transformed in the wake of having spent a single night with the children he or she is watching. The prototype for "the babysitting movie" found it genesis with 1987's Adventures in Babysitting. The Sitter, directed by David Gordon Green (of Pineapple Express fame), follows the blueprint for this type of film very closely.
Like the protagonist in Adventures in Babysitting, Chris Parker (Elisabeth Shue), Noah Griffin (Jonah Hill) is saddled with three unruly kids who could not give a single fuck about his demands. Granted, in Adventures in Babysitting, one of those kids is not a sibling of the two she is supposed to be looking after and are not nearly as young as the charges Noah is responsible for. However, the similarities in terms of obstacles to overcome and desires to fulfill are uncannily comparable.
Like Chris, Noah is infatuated with an object of desire who does not reciprocate his feelings with the same degree of intensity. Marisa (Ari Graynor, who seems fond of playing a vacuous asshole) is a girl who, as Noah puts it, "occasionally lets [him] stick [his] head in her crotch." But he can't see her for what she is until after she has put his life at risk by asking him to pick up some cocaine from a "zany" drug dealer named Karl (Sam Rockwell), who, for some reason, runs his operation out of a giant gym for bodybuilders. You see, involving crazy, unreasonable villains is absolutely key to a babysitting movie. This plight is similar to Chris', after she and the kids accidentally hide in a car that is in the process of being stolen (such an 80s crime, by the way) and end up in the "kooky" world of auto thieves, ultimately involving a stolen Playboy that nearly gets them killed. But nearly getting killed is all part of the fun in babysitting movies.
With numerous, seemingly inconquerable encumbrances to achieving the basic goal of keeping the kids safe, the most important part of the backstory in a babysitting movie is that it is set in a "dangerous" metropolitan city. For Adventures in Babysitting, that city is Chicago, whereas in The Sitter, it's New York, specifically Greenpoint in Brooklyn (which is possibly the least scary place in Brooklyn, unless you're afraid of white and/or Polish people).
But the single most significant element of a babysitting movie is that the babysitter must somehow, during the course of the night, find a new love interest to substitute for the dickhead he or she has been pursuing for the majority of the story. For Noah, that love interest is Roxanne (Kylie Bunbury), a former classmate with a shared zeal for astronomy. Just as Chris conveniently meets her stand-in boyfriend at a college party, Dan (George Newbern), an implausibly nice guy who gives her and the kids a ride home, so, too does Noah find a replacement of his own. And so, there you have it: The Sitter is basically a revamped version of Adventures in Babysitting--but that isn't to say it isn't a worthwhile and faithful rendering of the babysitting genre that was established by a seminal 1987 film.