Deborah Kerr's singing was dubbed by Marni Nixon, who also dubbed her in The King and I (1956) the previous year.

Deborah Kerr and Cary Grant improvised many of their scenes throughout filming, and a number of lines that made it to the final cut of the film came from the actors' improvisation.

References to this movie in Nora Ephron's Sleepless in Seattle (1993), revitalized interest in the film, and led to 2 million additional sales of the 1957 classic on VHS.

Ingrid Bergman was the first choice to play Terry McKay.

Nickie and Terry make their conditional promise to meet in six months at exactly the halfway point of the film (59-1/2 minutes into the 119-minute movie).

Deborah Kerr plays Terry McKay, previously played by Irene Dunne in Love Affair (1939), of which this film is a remake - both were directed by Leo McCarey. The year before this film was made, Kerr played Anna Leonowens in The King and I (1956), also a role that had previously been played by Irene Dunne in the black-and-white classic Anna and the King of Siam (1946). "The King and I" is a musical based on the same book.

A Bollywood film with the title Mann (1999) starring Aamir Khan and Manisha Koirala was inspired by this movie.

Continuity

Nickie walks past the Empire State Building at night after the concert, but when he looks up at the building, it is seen in daylight.

At the end, Nickie is drying Terry's tears with his right hand. In the next shot, he is using his left hand.

When Nickie sees Terry in the theater, she has a fur coat over both shoulders and her left hand on the middle of the seat back in front of her. In the next shot, only her right shoulder is covered and her hand has moved to the corner of the seat.

When Terry McKay is teaching the little kids to sing, two of them go and do a dance, then walk back around and behind the little girl. In the close-up of the cute little blond girl there is no-one behind her, and in the next shot the boy and the girl are there behind her again.

Just after Nickie and Terry both receive their telegrams on the ship's deck, the light source changes position on them between shots.



Incorrectly regarded as goofs

In both the school and the apartment, Terry has no visible means of getting around. However, just because the viewer does not see "visible means", it does not mean they don't exist.

Nickie does a painting of Terry and his grandmother who are both wearing the same shawl at the same time. This is not an error - it's artistic imagination.

On the ship's deck, Nickie suddenly says "What?" Terry replies "What?" Carey says, "What? What?", then laughs. Clearly, they had messed up the lines but then continued. For some reason, the director left it in the film rather than re-shooting it. But it's really not an error, since Terry does the same thing to him later in the film. It's her way of breaking the moment, changing the direction of Nickie's conversation.



Revealing mistakes

Just after Terry and Nickie get their telegrams on deck, a whale can be seen repeatedly breaching in the background loop of the ocean scene.

When Terry is conducting the children, the song they're singing is in 4/4, but she conducts it as if it were in 2/4.

An open-water shot of the Constitution shows the wake from the camera boat.



Crew or equipment visible

A camera shadow falls on a man and a plant when Terry comes out of the dress shop.



Errors in geography

The street lamp shown near the playground just before Terry is seen in the classroom, is not of a design used in New York City.



Character error

When Nickie enters Terry's apartment, he calls her "Debbie".

Terry moved to a new apartment after becoming paraplegic, yet she chose an apartment where she has to descend two steps between the door and the living room.