Producer Nancy Meyers once said of the casting in this film of actor Sam Shepard: "From the beginning, we were told to forget trying to get Sam to portray a character who doesn't enter the film until the third act. But we sent the script care of a True Value Hardware Store in Virginia, and two days later he said he'd do it".
Writer-producer Nancy Meyers once said of this film: "Our movie is about someone who never planned on motherhood. The comedy comes from J.C.'s ineptness to deal with this surprise. Ten years ago [c. 1977], Baby Boom (1987) would have probably starred a man, because not until recently, with the great female drive toward careerism and success, would it be believable that a woman could be so ill-prepared for motherhood."
At the end of the film, the credits list: "For Annie", who is the little girl sitting in the vet's office at the end (with her dog). This is actually Annie Meyers-Shyer, daughter of the directer Charles Shyer. In Disney's 1998 version of The Parent Trap (1998), which was directed by Charles Shyer's wife, Nancy Meyers, the twins played by Lindsay Lohan in the film were named after the real Annie Meyers-Shyer and her sister, Hallie Meyers-Shyer. However, at the end of this film, the credits list "For Hallie" instead.
In Diane Keaton's biography "Diane Keaton: The Story of the Real Annie Hall" by Jonathon Moor, it states: "On the first day of shooting, when Diane walked onto the set the whole crew stopped and stared. Used to her highly individual rummage-sale look they couldn't believe this sophisticated, glamorous lady with a body was the layered, hidden Diane everyone knows. Someone, in total admiration, said to her, "You look like...." "A female of the species?" laughed Diane".
"It's played like a '40s comedy" according to Time Out. The picture was inspired by such 1930s and 1940s era comedies as Bachelor Mother (1939) and Woman of the Year (1942). The production notes for this picture stated that films from the 1930s and 1940s were used as a model for the movie. Writer-producer Nancy Meyers once said: "I always loved how Roz Russell [Rosalind Russell] and Katharine Hepburn portrayed working women. They wore wonderfully tailored suits, and always carried envelope bags under their arms as they walked through their offices dishing out orders".
The infant Elizabeth Wiatt was actually played by two seventeen month old twin babies, they being Michelle Kennedy and Kristina Kennedy. The then bubs actually reprized their role as the kiddie in the subsequent Baby Boom (1988) TV series.
One of two role-reversal baby films of the mid-late 1980s that were top-billed by a star who was last named "Keaton". Diane Keaton starred in Baby Boom (1987) whilst Michael Keaton headlined 1983's Mr. Mom (1983) about three years earlier. The two actor-comedians [to date, September 2013] though have never collaborated nor been star teamed together on a filmed production, despite their same last name, which is the same as silent film comedian Buster Keaton.
According to the American Film Institute: "To film Elizabeth sleeping, crew members were required to darken the set until the baby was asleep, at which point the lights would be gradually raised and the camera would begin rolling."