Julia Jones (Alyson Hannigan) is an obese woman, who dreams of marrying Napoleon Dynamite, but even in her dreams she is rejected. Writing in her diary, she thinks she will never find her true love. Julia goes outside and dances to impress men on the streets. It doesn't, as her obesity gets the best of her.Later on, Julia goes to work at her dad's Greek diner. Her dad, Frank, suggests she gets married to someone of the same heritage as her. Julia is half Greek (her dad, who is actually portrayed as an African-American), half Indian (her mom) and half Japanese (her Japanese sister). He suggests Nicky, an ugly, greasy man. She then meets the very British Grant Fockyerdoder (Adam Campbell), with whom she forms an instant attraction. When Frank yells at Julia to get an order, she turns to respond and hits Grant over the head with the coffee pot she's holding, knocking him to the floor. She turns around only to find his table is suddenly empty and figures he ran away.Julia needs help and goes to see a love therapist, Hitch. Hitch rejects her at first but reluctantly agrees to help her. Julia explains about the man at the diner and thinks it will be impossible for him to fall in love with her. Hitch takes her to a garage where she gets "pimped out" into a slim attractive woman. She earns a spot on a reality television dating show called The Extreme Bachelor, the bachelor turning out to be Grant, the man she met in the diner. Grant greets all the women and is asked to eliminate the losers, which he does by shooting them. Julia is the last woman standing and is rewarded with dinner for two at a restaurant called "A Restaurant".After their meal, Julia and Grant head back to her apartment, where they have sex. Julia takes Grant to meet her parents. There is immediate tension between Frank and Grant. Grant goes to the bathroom to see Jinxers, the family cat, defecating loudly and continuously on the toilet. Things get a lot worse when Grant attempts to open a bottle of champagne. The cork hits a vase that contains Frank's mother's remains, and the problems only get worse when Jinxers begins humping the skeleton.Later, Grant takes Julia to Tiffany & Co., where they turn on the lights to reveal the salespeople ready to let her pick whatever she wants. Grant then confesses he loves her and proposes to her. Julia happily says yes. Then, Frodo, Gandalf, and the others try to pawn off a ring, with Gandalf pleading that the ring could "destroy all evil". Ignoring him, Frodo accepts the offer of $50. The hobbits then turn and repeatedly kick Gandalf in his "precious" (balls) and run off to "get some wine coolers... and hookers!" Now it's Grant's turn to take Julia and her family to meet his parents. This meeting doesn't go well either, as Roz, Grant's mother, informs everyone that Grant lost his virginity to their gay housekeeper Eduardo. Frank secretly brings Nicky along, telling Julia she has no choice but to marry him. Julia runs off, devastated. Later, Frank has a one-on-one basketball game with Grant's father, Bernie. Things get bad when Frank gets a huge taste of Bernie's chest hair.The next day, Julia and Grant go to a wedding planner named Jell-O, who has a massive butt. Jell-O suggests they go to Taco Butt, but they want something a little fancier. At first she is offended but when Grant tells her that he and Julia have already taken care of the other things listed for the wedding, Jell-O tells them that she wanted them to see what she had booked for the entertainment which was her dancing. She does some dance moves and backs up towards them with her massive rear and crushes them. Julia finally gets the chance meet Andy (Sophie Monk), Grant's best man, at the swimming pool. Of course, Julia assumes Andy is a man, but she is really a woman and is a lot more attractive than Julia. Julia is even more horrified when she finds out that the two were engaged three weeks ago. Andy helps Julia shop for her wedding dress. At the dress store, Julia hits her head on a power box and finds that she can read people's thoughts. Julia finds from reading Andy's mind that she still has feelings for Grant and plans to split the two of them up. Julia and Andy fight each other, Kill Bill-style. Julia grows depressed, fearing that she'll always be a lonely fat girl. She goes back to Hitch and tells him about Andy. Hitch reckons she doesn't stand a chance against Andy - but if she does, then everything will be fine in the end. Julia grows confident again and figures that she just has to make it through the wedding rehearsal at her dad's diner; then, only one day until their wedding. There, Andy shows up and accuses Grant of using Julia to get over her, but Grant ignores her.The big day has arrived, but unfortunately, Julia wakes up with a big pimple on her face. She eventually pops it, blowing her to the back of the room and knocking down a wall, but she is late for her wedding. Meanwhile, Andy finally tells Grant how she feels about him, and that Julia doesn't deserve him. She wants to marry him but Grant steps up and says he wants Julia. Andy ignores him and kisses him. Grant pushes Andy off and sees Julia, who has caught them in the act and runs away.Days later, Julia goes back to her apartment and is surrounded by balloons, gifts, and letters from Grant. She cannot forgive Grant, and agrees to marry Nicky. Once at the altar with Nicky, Julia is regretting it and has flashbacks about her and Grant. Frank, realizing that Julia is unhappy, stops the wedding and tells her she doesn't want Nicky. Grant is the one for her (he saw it in her flashback). Frank shows Julia a magazine with a picture of Grant and a message. It says to meet him on the rooftop of her apartment building. After an epic journey - throwing Andy down a stairway, bashing someone on the head with a baseball bat to get their bike - she gets there, only to find she just missed Grant. She leans her hands on the railings, causing it to snap and falls right into Grant's arms. It is very emotional but they get back together and get married, with Hitch officiating. Andy and Nicky meet at the wedding, and fall in love. Meanwhile, Grant and Julia leave in a horse and carriage. Julia also gets a present from her mother-in-law: a vaginal thermometer which apparently has been in their family for generations and is regarded as good luck when it's not washed.The film ends with Grant and Julia attending their honeymoon on Kong Island. They see a woman, Anne, tied to two pieces of wood. King Kong comes on and rips off her dress, leaving her clad in a leopard print bikini. Kong then gropes her, she says "I like hairy guys" and Kong roars and flattens her.