Plot
Growing up in the Bronx, Jill Sadelstein repeatedly attempts unsuccessfully to capture the attention of her gifted twin brother Jack by injuring him or repelling others from him. As an adult, Jack is a successful advertising executive, residing in Los Angeles with his wife Erin, their biological daughter Sofia, and their adoptive son originally from India, Gary, who compulsively tapes various objects to his body. Conversely, Jill is unemployed and lives alone in their childhood home, which she inherited following their mother's death the previous year.
Visiting Jack for Thanksgiving, Jill announces her intentions to depart at the end of Hanukkah, having an open-ended plane ticket, much to his consternation. At dinner, her obnoxious behavior embarrasses a homeless guest, Otto, as well as Erin's parents, Carter and Bitsy Simmons. Jack frustratedly snaps at her, and she flees into the woods with her pet cockatoo Poopsie. Erin demands that Jack apologize to her, which he reluctantly does.
Jill completes a checklist of activities that she has planned for her visit. Among the activities listed is appearing as a contestant on The Price Is Right; she receives various consolation prizes after unintentionally incapacitating herself while spinning the Big Wheel in the Showcase Showdown. While out horseback riding, she proves to be too massive for a pony that collapses under her weight immediately after she mounts it. When she answers her ringing cellphone during a movie, Jack reprimands her, and she tearfully departs.
Deciding that Jill needs a romantic partner, Jack, aided by Gary and Sofia, encourages her to try online dating. She is initially unsuccessful until Jack edits her profile on her behalf and uploads it to Craigslist, which proceeds to garner over 100 responses. A person nicknamed "Funbucket" meets her at a high-end restaurant, but a few minutes into their evening, he retreats into the men's restroom and hides there until she leaves. The staff of Jack's company, Sunny & Sadelstein, throw him a birthday party. Jill attends, but disgraces herself along with Jack and his colleagues, resulting in her ejection.
Meanwhile, Jack tries to cast Al Pacino in a Dunkin' Donuts commercial for their newest menu item, the Dunkaccino. At a Lakers game, Pacino ignores Jack but becomes infatuated with Jill. He gives her his phone number and invites her to his home, where she accidentally destroys his Oscar statuette. Uninterested in him, she promptly departs. Jack's Mexican gardener Felipe, also smitten with her, introduces her to his family at their annual fiesta. She immediately connects with everyone, including his children, as he has been a widower since the death of his wife 4 years earlier; however, after trying Mexican food for the first time, she suffers a severe case of diarrhea.
Pacino agrees to work on the Dunkaccino advertisement on the condition that he has another date with Jill, so Jack invites her to accompany him and his family on a cruise. She insists on bringing Poopsie, despite the cruise line's strict anti-pet policy. At sea, Jill and Poopsie irritate everybody on board. When Jill repeatedly rebuffs Pacino, Jack disguises himself as her and flirts with him on her behalf. Suspecting that her invitation was only to convince Pacino to do the advertisement, she phones Jack and hears Pacino in the background. Dejectedly arriving home in the Bronx on New Year's Eve, Jill discovers that the bank has foreclosed on her home because she discarded numerous bills that she mistook for junk mail.
Now homeless, Jill encounters a group of former schoolmates, led by class bully Monica, at a restaurant. Jack arrives with his family, and the siblings reconcile via their invented secret language. Monica attacks Erin, but Jill shields her from Monica's wrath. Afterwards, arriving at Jill's house, the group encounters Felipe, who has followed Jill and decorated the house. Pacino arrives dressed as Don Quixote, his character in a Broadway production of Man of La Mancha, and reminds Jill that although he still cares about her, other men deserve her more than he does. She turns to Felipe, who confesses that he loves her, and they start a relationship.
Ultimately, Pacino disapproves of Sunny and Sadelstein's commercial, which features him rapping, and instructs Jack to destroy all iterations of it.