Architect Steven Kovacs (Matthew Broderick) experiences a turbulent period after a failed marriage proposal to his girlfriend Robin Harris (Leslie Mann). Seeking advice from his well-meaning but reckless friend Rick (Jack Black), Steven resorts to bribing cable installer Ernie "Chip" Douglas (Jim Carrey) in exchange for complimentary movie channels. However, Chip's arrival is anything but timely—he shows up several hours late while Steven is in the shower, and it’s revealed that Robin has forced Steven out of his home, which Chip discovers through the change in billing.
Eager to form a bond, Chip convinces Steven to spend time together and brings him on an impulsive trip to the city's central satellite dish. During their outing, Chip opens up about his childhood, explaining how he was raised by television in the absence of his single mother. Although he speaks with a slight lisp, his feelings are hurt when Steven mentions his brother is a speech therapist, leading to tension between the two.
As their friendship unfolds, Chip’s behavior begins to invade Steven's life. From crashing a basketball game, where his aggressive playing style shatters a glass panel, to flooding Steven's answering machine with calls, Chip proves to be more than just a new friend. Taking a cue from Chip, Steven invites Robin over to watch "Sleepless in Seattle," but fate intervenes as the cable goes out—prompting him to call Chip, who conveniently waits outside his door. To regain access to his TV channels, Steven reluctantly promises to spend more time with Chip.
Their exploits lead to a dramatic evening at Medieval Times, where the two share a comedic yet competitive jousting match, and afterward, Steven is perplexed to find that Chip has installed an extravagant home theater system as a token of their burgeoning friendship. Despite declining the lavish gift, Steven agrees to host a gathering for Chip's other friends, believing he can return the system afterward. In a wild turn of events at the party, Steven finds himself sleeping with a young woman—only to discover, thanks to Chip, that she was a prostitute named Heather.
Angry and feeling deceived, Steven confronts Chip, leading to a dramatic fallout. Determined to fix things, Chip seeks out Robin, now dating another man, Owen Wilson. In a twisted act, Chip inflicts violence upon Owen in a restaurant’s restroom and installs a new cable package at Robin's place, falsely presenting it as a gift from Steven. This action inadvertently rekindles Robin's interest in Steven, but when Chip boasts about his interference, it prompts Steven to end their friendship.
Distraught by Steven's rejection, Chip embarks on a mission of revenge, which spirals out of control. He frames Steven for possession of stolen property, leading to an arrest facilitated by a police officer Chip manipulated. After being bailed out by his father, Earl Kovacs (George Segal), Steven faces further humiliation when Chip dines with his family and openly taunts him during a game.
The next day, Steven is unceremoniously terminated from his job after Chip leaks a private conversation, revealing Steven’s disparaging views of his boss. Determined to end the madness, Rick investigates Chip and uncovers his troubling history of stalking customers and using TV character names as aliases.
As the climax builds, Chip announces he is visiting Robin, and Steven must race against time to find her. The chase culminates at the satellite dish, where Chip holds Robin hostage amid a torrential downpour. After an intense struggle, Steven manages to save her, leading to a final confrontation with Chip. As the police loom, Chip makes a shocking declaration about needing to "kill the babysitter" to prevent others from experiencing his fate before performing a reckless dive off a ladder, inadvertently causing a citywide television blackout.
In a twist of fate, Chip survives with an injury and is airlifted away, leaving behind a haunting smile as he questions a paramedic about their friendship, hinting that his obsessions may never truly fade.
