The film unfolds with laser focus on Lenny (Ronald Bronstein), a divorcee in the Big Apple, during a two-week arranged custody of his elementary-aged sons. Juggling his job as a theater projectionist, two hyperactive young boys and a stale relationship, the demands Lenny must rise to meet become progressively more stressful to fill. The Safdies themselves based it loosely on experiences they'd had with their father in New York as children.
- Adult Fear: A major tone shift happens when the boys essentially go comatose from ingesting Lenny's sleeping pills. Lenny is, understandably, terrified during this time.
- Anti-Hero: Lenny spends most of the film this way, engaging in irresponsible parenting practices such as leaving his kids alone outside of their school for progressively longer periods of time. By the movie's end, he's arguably become a Villain Protagonist.
- Black Comedy: Lenny's Bumbling Dad tendencies are typically played for laughs, at least at the start.
- Blatant Lies: Lenny telling a homeless man that he has no money, only to do a handstand a couple seconds later that sends a rain of change out from his pockets.
- Bumbling Dad: The struggles to maintain a job and an already unstable relationship as a divorced father during your brief custody period leaves Lenny doing bumbling things like walking to pick up his kids from school with three ice-cream cones melting in one hand.
- The Cameo: Benny Safdie gets a brief cameo as one of the theater projection workers.
- Cerebus Syndrome: The movie is a great example of a slow-burning character study, as Lenny goes from a lovable, if inadequate, father figure at the film's beginning to a self-serving psychopath who kidnaps his own children because they're the only thing left in his life that makes him happy.
- Dream Sequence: Lenny dreams towards the end of the movie that a giant mosquito was sucking his blood as he slept.
- The Kindnapper: Lenny ultimately becomes this in the end, kidnapping his own children from their mother's caretaker, hastily moving out of his own apartment to avoid being found, and forcing his children onto an aerial tramway to escape. He does this while still acting normally, if a little more urgently, because he simply wants his children to be a part of his life.
- Leave the Camera Running: The whole film is shot guerrilla-style, with the action in many takes having fizzled out long before a cut. A notable example is the final shot of the movie, which lingers on a tramway as Lenny takes his kids far away from their mother's custody.
- MayDecember Romance: The middle-aged, greying Lenny appears to be in a relationship with the young, freckled Leni.
- One Steve Limit: Lenny is the film's protagonist and the boys' father. Leni is the man's girlfriend, though you might not be able to tell by the pronunciation.
- Realistic Diction Is Unrealistic: Typical to the Safdie brothers' style, this trope is averted. Daddy Longlegs is classifiable as mumblecore because of the realism and interruptions in its dialogue.
- Unusually Uninteresting Sight: Two young boys buying groceries without accompaniment of a guardian, a man carrying a fridge backpack-style onto a tramway, you name it.
- Your Cheating Heart: The exact nature of Lenny and Leni's relationship is undefined, though he does hook up with a random girl at the bar during a time where she probably considered them together.