When Hallie arrives in London and meets Martin at the airport, at the point where the two begin their greeting, you can see Lindsay Lohan's mother holding her brother Cody Lohan, and beside her is Lindsay's other brother Michael Lohan and sister Ali Lohan. (If you watch closely, Ali can be seen turning around to watch her sister, then Lindsay's mother turns to look as well.)
When this movie is shown on Disney Channel, the scenes where Hallie pierces Annie's ears and Annie (as Hallie) taking a sip of the wine are edited out. In addition, "Oh my God" are muted out in some scenes. When Annie (as Hallie) says "Oh my God... Oh my God!", Nick replying to her "Now you're starting to sound like your old self." is muted.
After Hallie arrives in London, her mother takes her to a photo shoot. Above this, we hear a cover version of "Here Comes The Sun" by The Beatles, one of the songs on their album "Abbey Road". As we watch Hallie and her mother on her way, they cross the same street the same way as The Beatles did for the cover photo of the album "Abbey Road". Even the cars on the side are the same.
The twins in this version are named after the daughters of director Nancy Meyers' and producer Charles Shyer, Annie Meyers-Shyer, and Hallie Meyers-Shyer, both of whom have small parts in the movie. Hallie plays a girl at camp at the beginning who asks where the Navajo bunk is, and Annie plays the towel girl at the hotel who brings Elizabeth the first aid kit. The character whom Hallie Meyers-Shyer plays, conversely, is named Lindsay, after Lindsay Lohan, the actress who plays Hallie and Annie.
The scene where Annie and Hallie are lying in bed and the camera pans from the moon, to the parents' picture, to the twins, took six hours to get right. Lindsay Lohan' had to change from Annie to Hallie, and back all the time.
The reaction of Nick Parker (Dennis Quaid's character) reaction to seeing Elizabeth (Natasha Richardson's character) for the first time in 11 years is identical to James Garner's character's reaction in Move Over, Darling (1963) upon seeing his missing wife after 5 years. In both films, the man is on an elevator with his current partner and leans over in disbelief as the door closes. James Garner's character in Move Over, Darling (1963) is also named Nick. James Garner actually copied the move in the elevator from Cary Grant who did the same thing in the movie My Favorite Wife (1940). When Cary Grant entered the elevator with his new bride Gail Patrick he was shocked to see his first wife Irene Dunne who after seven years had been declared missing at sea and presumed dead that very morning. Move Over Darling is a remake of My Favorite Wife. Dennis Quaid also does a very distinctive voice impersonation of Cary Grant in the scene following the camping trip.
Mara Wilson auditioned for the dual roles, but was ultimately passed over because producers felt she wasn't old enough to play the parts. Scarlett Johansson also tried out for the lead but lost out to Lindsay Lohan.
In casting the dual role of twins Hallie and Annie, director Nancy Meyers kept saying, "I'm looking for a little Diane Keaton... Diane is so alive on screen and that's what I wanted from the actress in these parts."
The opening and ending sequences each feature a love song performed by the legendary Nat 'King' Cole and his daughter Natalie Cole respectively. The opening scene has Nat 'King' Cole's "L-O-V-E" playing over images of Elizabeth and Nick's first wedding. The end credits have Natalie Cole's "This Will Be (An Everlasting Love)" playing over photographs of Elizabeth and Nick's second wedding.
To find the actress who would play Hallie and Annie, an exhaustive casting search was conducted in Boston, Chicago, Minneapolis, Atlanta, Miami, Vancouver, Toronto, and London, with open calls in New York and Los Angeles. Eventually 11-year-old Long Island native Lindsay Lohan was given the role.
Lindsay Lohan can be heard singing "Let's Get Together" as she walks into the elevator at the Stafford Hotel. This song is from the 1961 original. Similarly, the first few notes of "Let's Get Together" are played as the closing notes of music at the tail of the end credits.
The music that plays when Annie/Hallie do the "secret handshake" with Martin is the intro to "Am I The Same Girl" by Dusty Springfield, which include the lyrics "Why don't you stop and look me over.. Am I the same girl you used to know?"
The film states: "For Hallie" during the final credits, which is a dedication to 'Nancy Meyer''s real-life daughter, Hallie-Meyers Shyer. This is probably because of a pre-existing dedication in the 1987 film Baby Boom (1987), which was directed by Nancy Meyer's husband, Charles Shyer. However, the credits at the end of this film list "For Annie" instead.
In the scene where Hallie tells Annie about the idea to switch places, as the girls go back to bed, if you look very closely on the left side you can see Lindsay Lohan's acting double, Erin Mackey momentarily, right after Annie says "After all these years."
From the opening of the film we find out that the parents were married on 8 January 1986. Nicholas Parker was 24 and Elizabeth James was 23. Elizabeth's occupation is listed as artist, while Nick's is listed as Viticulturist.
The name of the hotel, The Stafford, is a reference to the name of a boy in the original The Parent Trap (1961). He is the boy Hayley Mills' character, Susan, is talking to at the camp dance, when the back of her dress was cut off by twin-sister, Sharon.
The name Meredith Blake is a reference to a male character in "Five Little Pigs", a story written by Agatha Christie. An adaption of that story was produced for the TV series Agatha Christie: Poirot (1989).
When Hallie is in London talking to Annie on the phone she uses "Mildred Plotka" as her fake friend's name to her mother. Mildred Plotka was the real name of the character played by Carole Lombard in the classic screwball comedy Twentieth Century (1934).