Yalies, in their do-it-all glory, have a lot in common with the ambitious star of “2 Days in Paris,” Julie Delpy. Delpy, who previously starred opposite Ethan Hawke in “Before Sunrise” and “Before Sunset,” wrote, edited, composed and starred in “2 Days in Paris,” while also casting her own parents, ex-boyfriend and cat. And the outcome would make even the most compulsive Eli proud: Delpy delivers a hilarious and whimsical look into her hometown and the nature of romantic relationships.

“2 Days” concludes a summer-long obsession with Paris at the cinemas. But while “Ratatouille” treated the city with reverence and “Paris Je T’aime” with admiration, Delpy appears to regard Paris with bemused contempt. Delpy’s Paris is one of sexual aggression, psychological instability and amusing idiosyncrasies. Grounding us within the bizarre surroundings is the central couple: Delpy plays Marion, an endearing, spontaneous and ultimately insecure photographer with bad eyesight (irony alert!). Delpy is spending two days in Paris at her parents’ house with boyfriend Jack (played by Adam Goldberg, of “Entourage”), who is a jealous, sarcastic Francophobe who hates taking the subway. He feels like being with her is like “dating public television,” while she just can’t believe that he’s the one.

The film is oddly similar in feel to “Before Sunrise,” but instead of centering on what brings people together, “2 Days” muses on what can tear them apart: jealousy, lies and insecurity. Delpy and Goldberg feel like a real couple, perhaps because the pair dated a decade ago. Their smooth and snappy delivery is the highlight of the movie.

Both performances are spot on: Delpy cleverly reveals the darker side of the typical Parker Posey-leading-indie-lady, while Goldberg keeps his shtick funny but in check. The characters are so well-drawn that when Marion lies about a previous relationship a half hour into the film, it’s immediately clear why she would do it and how Jack will react before any of it plays out.

The film only features two other main characters: Marion’s parents Jeannot and Anna (played by Delpy’s real life parents). The parents serve as more than comic relief (though they do also provide that) by granting Delpy her finest moments: Marion’s mesmerizing rant about her cat would have been nothing without Anna’s shocked expression and sobbing interjections.

Moments like the cat rant are what make the movie work: funny or poignant scenes that are revealing of the characters and their relationship without driving a “plot” in the conventional sense. Unfortunately, the last 10 minutes stand in stark contrast to the rest of the film in this respect. At the end, Delpy tries to make too much out of the film, using a literal and expository voiceover (which had previously only been used for witty observation) to reveal some deeper truth about relationships, which lay beyond the reach of Delpy’s screenwriting ability. Unlike the ambiguous ending of “Before Sunset,” one of the best in recent memory, “2 Days” begins to transform into a typical breakup-make up comedy, ending on a frozen frame of spontaneous bliss.

But, while the ending is frustrating, it certainly does not negate the brilliance of the previous 80 minutes. And it certainly does not negate Delpy’s achievement. Famous for being passed up for roles, most recently for the female lead in “The Da Vinci Code,” Delpy proves her resilience and far-reaching talent yet again. But if other directors don’t take note, there’s no doubt now that Delpy will be able to use her multi-faceted talents to provide another stunning turn (and perhaps Delpy’s goldfish should keep his calendar open).