Despite the film's lukewarm reception, Schwarzenegger and Thompson received Golden Globe nominations for their performances. The film's theme song, Patty Smyth's "Look What Love Has Done" was also recognized, going on to be nominated for the Academy Award for Best Original Song. It is also Schwarzenegger's third collaboration with DeVito, following 1988's Twins and preceding 1993's Last Action Hero, and second with Pamela Reed after 1990's Kindergarten Cop.
Austrian Research geneticist Dr. Alex Hesse (Arnold Schwarzenegger) and his OB/GYN colleague Dr. Larry Arbogast (Danny DeVito) have invented a fertility drug, "Expectane", that is supposed to reduce the chances of a woman's body rejecting an embryo and thus prevent a miscarriage. Unfortunately, they are not allowed to test it on women since the Food and Drug Administration has not yet approved the drug; so Hesse and Arbogast cannot move forward in their research.
In response, Hesse breaks into the laboratory and locks himself in. The head of the review board, Noah Banes (Frank Langella), informs Arbogast that while the FDA has denied their team the right of human experimentation, the team has managed to receive a donation from fellow geneticist Dr. Diana Reddin (Emma Thompson) from the ovum cryogenics department. When Hesse questions the chances of a woman taking an unapproved drug during pregnancy, Arbogast reveals that there is no need to identify the gender of the experiment and convinces Hesse to impregnate himself, using an ovum codenamed "Junior".
That night, Hesse has a nightmare in which his potential offspring has his own face pasted onto it. That day, he complains to Arbogast that his nipples are hurting him. Later, the normally aloof Hesse inexplicably lightens up and chats incessantly about walks, massages, and naps. Reddin tells Hesse that being a woman is not as great as it sounds, citing the menstrual cycles which do not stop until menopause. Meanwhile, Arbogast's pregnant ex-wife, Angela (Pamela Reed), wants him to be the doctor delivering her baby. Hesse begins to wonder what it would be like to be a father and watches some television commercials to have himself a good sobbing. He later begins overreacting, with Angela noting his practice of "mixing cuisines".
It is revealed that the "Junior" ovum is actually from Reddin's own body, making her the mother of Hesse's child. Banes wants to take credit for the experiment despite having no role in it. Arbogast disguises Hesse as a woman and hides him in a retreat for expecting mothers outside the city, passing off his masculine appearance as past anabolic steroid use. Eventually, after a visit from Reddin, Hesse experiences abdominal pain due to the damage that the baby is doing to his abdomen. While shut away in his resort room, Hesse calls both Arbogast and Reddin. As Reddin rushes to the resort from the laboratory, Arbogast calls a fellow doctor and tells him to evacuate the hospital and prep it for an emergency c-section for Hesse, but a hospital staffer overhears the doctor's conversation and alerts Banes about it. Banes calls the media to the hospital, to take credit and become famous, but Arbogast's fellow doctor alerts him about the media and Arborgast makes a detour to get a decoy for Hesse so he can have a private c-section.
When Arborgast's car arrives at the hospital, he disappoints the media when he brings out his own pregnant ex-wife. Banes, who had summoned the university dean and the press to witness the world's first pregnant man, is discredited and fired. Meanwhile, Reddin and Hesse have snuck to the back of the hospital and use the fire escape to get in. While acting as Hesse's decoy double, at the hospital, Angela goes into labor. Hesse has an emergency caesarean section, where he is given an epidural even though he's at high risk as is the baby. Reddin, not being able to help Hesse through this time, is sent by Arbogast to keep Angela company. Reddin walks into the waiting room to find Angela in labor and ends up being her labor coach, since there's no hospital staff available. Hesse feels emotionally scared and horrible, as Arbogast and the other surgeon cut through the last few layers of tissue, to get to the baby, Arbogast announces that Hesse's water shows no signs of fetal distress.
Arbogast announces the arrival to Reddin, who is on hands and knees helping Angela cope with contractions. Reddin hands Angela over to Arbogast and rushes off to see Hesse as Arbogast has Angela prepped for childbirth. Reddin visits Hesse in the Post-op, getting her first glance at her baby, and together they decide to name the baby girl Junior. Arbogast delivers Angela's child and the two reconcile to raise the boy, Jake, as their own.
In the final scene, the two families are on a beach on vacation celebrating the birthdays of Junior and Jake. Reddin is heavily pregnant with her and Hesse's second child, and when Angela mentions that she would like to have another baby but does not want to go through pregnancy again, they all begin trying to convince a reluctant Arbogast to carry the child.Arnold Schwarzenegger as Dr. Alex Hesse
Danny DeVito as Dr. Larry Arbogast
Emma Thompson as Dr. Diana Reddin
Frank Langella as Dr. Noah Banes
Pamela Reed as Angela
Aida Turturro as Louise
James Eckhouse as Ned Sneller
Megan Cavanagh as Willow
Christopher Meloni as Mr. Lanzarotta
Brianna & Brittany McDonnell as Diana Jr.
Ryan & Zachary Doss as Jake
In North America the film grossed slightly more than half its budget ($37 million vs. $60 million); worldwide it grossed $108 million.
The film received negative reviews with a 34% approval rating on Rotten Tomatoes, with an average score of 4.7 out of 10, based on 32 collected reviews.
Comedian and former Mystery Science Theater 3000 host Michael J. Nelson named the film the second-worst comedy ever made.
Notably Roger Ebert was a fan of the film, giving it 3½ out of four stars and maintaining that: "I know this sounds odd, but Schwarzenegger is perfect for the role. Observe his acting carefully in Junior, and you'll see skills that many 'serious' actors could only envy."
Ebert and his partner Gene Siskel gave the film "two thumbs up" on their television show.
In May 2007, Sandy Smith had launched an essay writing competition, asking entrants to attempt to prove that Junior could be considered the greatest movie of all time. He obsessively started collecting copies of the movie in November 2005, and eventually collected 24 copies. In February 2008, despite Sunday Herald covering the story, the competition received fewer entries than there were prizes offered. The essays submitted, and one commissioned from an academic essay writing company to Smith's own specifications, are available to read on the competition website.