Ian Lafferty, portrayed by Josh Zuckerman, is an eighteen-year-old graduate who embarks on a quest to connect with a girl online. He crafts a persona that makes him seem buff and charming, but in reality, he is quite the opposite—sweet and earnest. When he meets "Ms. Tasty," played by Katrina Bowden, he eagerly agrees to meet her in Knoxville, a vibrant city far from his home in Brookfield. Joined by his close friends, Lance, depicted by Clark Duke, and Felicia, played by Amanda Crew, they borrow a Pontiac GTO Judge from Ian's haughty older brother, Rex (James Marsden), without his knowledge.
Their journey to Knoxville becomes a chaotic adventure. Struggling with car troubles, they encounter a hitchhiker while the radiator in the Pontiac overheats. During a humorous attempt to fix the radiator by urinating in it, they unintentionally drive away the hitchhiker who felt neglected by Ian’s indifference. Meanwhile, as Ian and Felicia seek assistance, Lance stays with the car. They meet Ezekiel, portrayed by Seth Green, who arrives in a horse-drawn buggy alongside his Amish friends. They lend a hand in fixing the car and invite the trio to a Rumspringa party featuring a concert by Fall Out Boy, where Lance finds himself enamored with an attractive Amish girl, Mary (Alice Greczyn). They agree to return later to repay the favor.
However, the mischief does not end there. Ian’s frustrations boil over, leading to a mishap that lands them in jail after he throws a tire iron at a state trooper’s vehicle. They are released thanks to Mary, who pays their bail. Afterward, the group checks into a hotel equipped with an array of role-playing rooms. Just as their plans begin to unfold, Rex angrily confronts Ian, forbidding him from seeing Ms. Tasty. In a bid to appease Rex, Ian pretends to be gay, which gives him the green light to meet Ms. Tasty, as Rex hopes this encounter will sway his brother's interest.
Upon meeting Ms. Tasty in person, however, Ian's dream takes a dark turn. She attempts to seduce him, but that allure quickly morphs into a threat, as her deranged boyfriend, Bobby Jo (Dave Sheridan), brandishes a gun. It's soon discovered that they are involved in a chop shop operation and plan to rob Rex's Pontiac. Amid the ensuing chaos, Ian manages to rescue Felicia, who courageously reports their situation to the authorities. Ms. Tasty's getaway attempt is thwarted by some familiar high school adversaries, leaving Bobby Jo to face the consequences after a confrontation with Ian.
Ultimately, in a twist of fate, Lance decides to abandon the journey home for an Amish life with Mary. Meanwhile, Ian and Felicia acknowledge their feelings for one another. On that momentous New Year's Eve, Ian shares his first intimate experience with Felicia. In a revealing moment, it's suggested that Rex's aggression may stem from his own repressed identity. The film closes with a heartwarming shot of Lance and Mary on their wedding day, while Ian and Felicia, alongside a humorous interlude featuring Ezekiel and Fall Out Boy debating their compensation, remind viewers of the unconventional journey they all embarked on together.
