The film marks the final franchise appearances of the main stars, Anna Faris and Regina Hall (who portray Cindy and Brenda, respectively), and concludes the original story arc. This was initially intended to be the final film in the Scary Movie franchise, until Scary Movie 5 was released by The Weinstein Company on April 12, 2013, in a different storyline, with Simon Rex, Charlie Sheen, and Molly Shannon in different roles.
Shaquille O'Neal and Dr. Phil wake up to find themselves chained to pipes in a bathroom. Their host, Billy the Puppet, reveals that the room is slowly filling with nerve gas with the only way out being to make a basket and get the saws, which have to be used on their feet. Unfortunately, Dr. Phil saws the wrong foot and faints, leaving the two to die.
Meanwhile, Cindy Campbell (Anna Faris) visits her former brother-in-law, Tom Logan (Charlie Sheen) in New York City. Her husband George (Simon Rex) has died, and her nephew Cody has enrolled in military academy, leaving her broke and lonely. Tom's attempted suicide results in his ingesting viagra, which greatly swells his penis and causes his death when he falls off the railing. Afterwards, Cindy takes a job to care for Mrs. Norris (Cloris Leachman), who lives in a haunted house. Next door is Tom Ryan (Craig Bierko), who runs into George's friends Mahalik (Anthony Anderson) and CJ (Kevin Hart), learning about their homosexual one-night stand. He is greeted at home by the arrival of his estranged children, Robbie (Beau Mirchoff) and Rachel (Conchita Campbell). Over the following day, Cindy bonds with Tom, confiding to him about George's death in a fateful boxing match. The two realize their newfound love, but are interrupted by a gigantic triPod which disables electricity and starts vaporizing the town residents.
Cindy converses in mock Japanese with the haunted house's ghost, Toshio (Garrett Masuda), learning that the answer of the invasion is his father's heart. While Tom leaves the city with his children, Cindy reunites with her friend, Brenda Meeks (Regina Hall), miraculously alive after her death. Following Toshio's directions, the two head to the countryside and end up in a mysterious, isolated community. They are captured and put to trial headed by Henry Hale (Bill Pullman). The result allows them to live but never leave the village. Meanwhile, an emergency United Nations meeting, headed by the eccentric U.S. President Baxter Harris (Leslie Nielsen), who is reluctant to stop reading "My Pet Duck", goes awry when a weapon scavenged from the aliens renders everyone stark-naked.
Tom and his children drive and find themselves in the middle of a war between the U.S. military and the aliens. Excited with the conflict, Robbie runs away, while Tom and Rachel are taken by the triPod. Back at the village, Henry is killed by the village loon, Ezekiel (Chris Elliott), revealing to Cindy that he fathered Toshio, who was killed during Cindy's boxing match. Cindy and Brenda are soon taken by the triPod and sent to the bathroom seen in the prologue. Cindy manages to get through Billy's challenge, but is threatened with the safety of Tom and his children, who are put to traps. Looking at a toilet with the "heart" nearby, Cindy realizes that Billy, through Henry's wife, is the true father of Toshio. Seeing how far Tom would save his children, Billy apologizes for the invasion and releases them. Robbie and Rachel are successfully returned to their mother (Molly Shannon), who is revealed to have married a much older man. Brenda also becomes acquainted with Billy's friend, Zoltar.
An epilogue set nine months afterward, narrated by James Earl Jones who is subsequently hit by a bus, reveals Brenda's giving birth to her child with Zoltar, Mahalik and CJ resuming their relationship, and President Harris being contented with his duck. Meanwhile, Tom appears in The Oprah Winfrey Show and wildly professes his love for Cindy by jumping around, throwing Cindy, and crushing Oprah's wrists.
As with the other films in the series, Scary Movie 4 parodies a wide array of movies and television shows."Dr. Phil" – Appeared in the very start of the movie, ending up his right leg cut off, forming the number 4.
Saw (franchise) – Billy the Puppet serves as the parody antagonist.
Saw – the opening scene with Shaq, Dr. Phil and the Billy puppet. The same set would be reused in future installments of the actual franchise.
Saw II – Cindy and Brenda both wear Venus Flytraps, and Cindy must retrieve a key hidden behind her eye.
The Village – Central parody
The Grudge – Main parody
War of the Worlds – Main parody
Million Dollar Baby – Cindy's boxing match against a female Mike Tyson.
Brokeback Mountain – CJ and Mahalik’s sexual encounter inside the tent.
Hustle & Flow – Cindy's brief first marriage.
Deuce Bigalow: European Gigolo – Tom Logan's penis gets attacked by a cat.
Scooby-Doo – Cindy unmasks "the creatures", discovering Old Lady Henderson and Pig Face Joe.
The Oprah Winfrey Show – Tom Cruise’s "jumping the couch" incident.
President Bush's 9/11 book reading incident – President Harris listening to a girl reading a book about a duck at the Edna R. Penhall Elementary School, while being informed about the alien attacks.
Final Destination - The freakish fatalities at the boxing match; also, James Earl Jones is run over by a passing bus while he narrates mankind's victory through love, similar to Amanda Detmer's character in the film.
King Kong – Kong is featured on the cover poster.
In its opening weekend, the film grossed a total of $40.2 million, the third best opening weekend of the Scary Movie franchise. It has the best Easter weekend opening weekend ever, beating Panic Room which made $30.1 million in its opening and also the second best April opening, only $2 million behind Anger Management's record. As of October 18, 2006, the film has grossed a total of $90,710,620 at the United States box office and $178,262,620 worldwide.
The film was released on DVD on August 15, 2006 in rated (83 minutes) and unrated (89 minutes) editions with deleted scenes, bloopers, and outtakes. About 1,581,754 units were sold, bringing in $22,308,989 in revenue.
Review aggregator website Rotten Tomatoes reports that 37% of 126 critics gave the film a positive review, with an average rating of 4.7 out of ten. According to the site's consensus, "[Scary Movie 4 is s]ure to inspire a few chuckles, but not enough to compensate for the recycled material from its predecessors." The film averaged 40 out of 100, based on 23 critics, on Metacritic, indicating "mixed or average reviews".
Stephen Hunter of The Washington Post stated that while "Scary Movie 4 never takes you close to death by laughter [...] it's funny enough to turn the hands on your watch much more quickly than you can believe." Nathan Lee of The New York Times' described the film as being "organized on the principle of parody, not plot, [...] it's an exercise in lowbrow postmodernism, a movie-movie contraption more nuts than Charlie Kaufman's gnarliest fever dream. It's cleverly stupid."
The film won a Golden Raspberry Award for Worst Supporting Actress (Carmen Electra, also in Date Movie).