During the first ice age, a caveman (Brendan Fraser) attempts to make fire with his girlfriend (Sandra Hess). An earthquake causes a cave-in that buries the two of them.
This segues into a present-day Los Angeles earthquake that awakens average teenager Dave Morgan (Sean Astin). He, along with his best friend Stoney (Pauly Shore), strives to attain popularity in high school but comes off more as a reject and an outcast. Dave is in love with Robyn Sweeney (Megan Ward), a sweet and attractive girl who has been his best friend since grade school, and until she reached "babehood" had been rejected by Dave on several occasions. Her boyfriend Matt Wilson (Michael DeLuise) is a dimwitted jock and school bully who is constantly responsible for making both Dave and Stoney the objects of ridicule by embarrassing them in various ways, usually directly due to Dave's growing affections toward Robyn.
One day, as Dave is digging a pool in his backyard, he comes across a chunk of ice that has the body of a man in it following an earthquake. They leave the ice block unattended in the garage and space heaters left on cause the ice to melt, releasing the caveman from the opening of the film. The caveman falls head first into the 20th century, discovering a garbage truck which he misinterprets as a mammoth from his time, and television which he discovers upon entering Dave's house. When the boys return home, they find hand paint covering the walls and the house is in disarray. Investigating a beeping smoke alarm, they discover the caveman in Dave's bedroom, attempting to start a fire "Indian-style" by rotating a stick in the center of a pile of kindling. At first, the caveman panics at the sight of them, but then Stoney quickly calms him by using the flame of a lighter to mesmerize him after he panics from the phone ringing. After bathing him and trimming him to look like an average teenager, Dave names him "Link" as in the missing link.
They manage to fool Dave's family into thinking he is actually an Estonian exchange student sent to live with them, and enroll him in school where Link's bizarre behavior and supreme athletic skills shoot Dave and Stoney to popularity by association, allowing Dave to get closer to Robyn, to Matt's chagrin. It soon becomes apparent that Stoney's bizarre attitude is having an effect on Link's actions and speech, which causes a rift between Dave and Stoney and after a fight with Matt at a skating rink, as well as an attraction developing between Robyn and Link. During a school field trip to a natural history museum, Link gets upset realizing that the cavepeople he knew are all dead and the gravity of his situation, but Stoney and Dave console Link that he is not without friends in this time, causing the trio to make a pact. Dave tries to send Link away, but a fight between him and Stoney cause Link to come running back. Stoney and Dave then make up. On prom night, Link is a hit at the party with Robyn as his date while Dave stays in for the evening. Matt breaks into Dave's bedroom and steals photographic evidence that Link is a caveman. As Dave and Stoney go after Matt and his friends, another earthquake happens. At the prom, Matt's plan to uncover the "freak" backfires as the information instead makes Link even more popular. Dave and Robyn make up, and the three boys lead the entire prom in an impromptu caveman-like dance.
After the prom, the students attend Dave's house for a pool party where Dave and Robyn kiss. Meanwhile, Stoney and Link follow clues similar to when they found him ranging from breast prints on the slider and paint covering the walls. They follow the muddy footprints to the bathroom and discover a beautiful cavewoman in the bathtub who turns out to be Link's girlfriend from the beginning of the film. He joins her in the bathtub as Stoney cheers them on and embraces her happily as she is also made to look like a modern human.Sean Astin as David "Dave" Morgan, a good-natured, tense, almost neurotic teenager who is in love with Robyn, despite losing his chance with her in grade school because he thought she was not attractive yet. He dreams of popularity more than his friends and is the most worried about being labeled as a freak if Link's secret ever got out. He is already labeled as a geek in the school.
Brendan Fraser as Linkovich "Link" Chomovsky, a caveman found in the 20th Century when Dave and Stoney dig up a block of ice in which he is frozen. He is very friendly, despite also being very fierce and aggressive in his mannerisms.
Pauly Shore as Stanley "Stoney" Brown, a loud, obnoxious Hippie/New Wave teenager who is a fan of the gameshow Jeopardy. His lease on life is profound and deeper than his thoughts seem to go. He is compassionate and quick thinking, able to soothe Link's primal instincts by showing him how to harness fire. He becomes Link's best friend and role model, eventually causing Link to imitate him.
Megan Ward as Robyn Sweeney, a kind, compassionate girl going out with the jock bully Matt Wilson. She attempts to maintain friendships with Dave and Stoney but is often put off by their childish mannerisms. She is already showing signs of growing tired of Matt's snobby and egotistical ways. She eventually realizes the depth of her friendship with Dave and breaks up with Matt after he starts bullying him.
Robin Tunney as Ella, a vain, self-centered girl and Robyn's best friend. She attempts to gain Link's attention by flaunting her 'gonzongas' at him. She is rebuffed, and learns that Link had a former love, and he has no interest in anyone else.
Michael DeLuise as Matthew "Matt" Wilson, a popular jock and notorious school bully who has made it his passion in life to torment, bully and humiliate Dave. He tends to keep his distance from Stoney who merely shrugs off his intimidation attempts. He is very stuck-up and the thought of Dave becoming more popular than he is causes a great deal of conflict, eventually causing him to lose the one thing Dave wants that he has; Robyn.
Encino Man is directed by Les Mayfield, a veteran of behind the scenes promotional documentaries, making his feature film debut. The film was shot in just 33 days in late 1991, which was considered a short schedule for a comedy.
Pauly Shore was known for his show Totally Pauly on MTV and Disney expected this would bring an existing audience to the film. The film tested well with teen audiences, and Mayfield thanked Wayne's World which came out a while before Encino Man for showing a comedy aimed at this demographic could do well.
Costume designer Marie France decided not to buy clothes; she instead custom-made the wardrobe for Stoney's and Link's characters. For Shore, she took his own unusual style and gave it a younger look. For Fraser, who stands at a height of 6' 3", it was a matter of practicality, easier than trying to find the sizes needed, and she dressed him in baggy knee-length shorts and oversized T-shirts.
The film received mostly negative reviews from critics. Encino Man holds a score of 16% on film review aggregation website Rotten Tomatoes based on reviews from 32 critics, saying "Encino Man isn't the first unabashedly silly comedy to embrace its stupidity and amass a cult following, but whether or not it works for you will largely be determined by your tolerance for Pauly Shore."
Despite the negative critical response, the film was a box-office success. The film took in $9,866,120 in its opening weekend coming 4th at the box office. The film went on to earn a total of $40,693,477 at the North American box office.
Pauly Shore's performance in Encino Man won him the Razzie Award for Worst New Star.
Link, again played by Fraser, makes a cameo appearance in the 1993 film Son-in-Law, which also stars Pauly Shore. Fraser also briefly appears as a soldier with the name "Link" on his fatigues in In the Army Now starring Shore.
In Evan Wright's book about the 2003 invasion of Iraq, Generation Kill, the US Marine company commander is nicknamed Encino Man, supposedly for his incompetence. In the 2008 HBO miniseries of adaptation of the book the officer is played by Brian Patrick Wade.
The 1999 South Park episode, Prehistoric Ice Man, was a parody of the film, wherein the boys find a man that has been frozen in ice since 1996. Everyone in the episode acts as though this is a breakthrough discovery, and a chance to find out what life was really like in 1996.