Despite the fact that the film is set during Christmas, studio head Darryl F. Zanuck insisted that it be released in May because he argued that more people went to the movies during the summer. So the studio began scrambling to promote it while keeping the fact that it was a Christmas movie a secret.
Maureen O'Hara was ultimately forced into her role against her will, as she had just returned to Ireland before being called back to America for the film. However, she immediately changed her sentiments upon reading the script.
20th Century-Fox studio head Darryl F. Zanuck was very much against making this film because he thought it too corny to succeed. He finally agreed to a medium-sized budget provided writer/director George Seaton would accept his next three assignments unconditionally. Seaton, who desperately wanted to get the picture made, agreed.
When Dr. Pierce explains Kris' belief that he is Santa Claus, he offers for comparative purposes a Hollywood restaurant owner who believes himself to be a Russian prince despite evidence to the contrary, but rather conveniently fails to recall the man's name. This was a reference to Michael Romanoff, owner of Romanoff's in Hollywood, a popular hangout for movie stars at the time.
The scenes of the Macy's Thanksgiving Day Parade are of the actual parade held in 1946. As such, careful preparation was necessary for the shots as retakes were obviously out of the question. 20th Century-Fox had cameras positioned along the parade route at the starting line at 77th Street, on Central Park West, on the 3rd floor of an apartment building at 253 West 58th Street, in Herald Square and on 34th Street at 7th Avenue.
In the untranslated dialogue with the Dutch girl, Santa Claus asks the child what she wants for Christmas the girl says she wants nothing, telling Santa she got her gift by being adopted by her new mother.
Unbeknownst to most parade watchers, Edmund Gwenn played Santa Claus in the actual Macy's Thanksgiving Day Parade held November 28, 1946. He fulfilled the duties of most parade Santas, including addressing the crowd from the marquee of Macy's after the parade was over. He was introduced to the crowd by actor Philip Tonge (he played Mr. Shellhammer in the movie) and he later unveiled the mechanical Christmas display windows to the accompaniment of Pyotr Ilyich Tchaikovsky's "Nutcracker Suite." This gesture symbolized the opening of the Christmas shopping season at the store.
According to Hedda Hopper's "Looking at Hollywood" newspaper column of May 3, 1947 "when the picture opens at the Roxy, Macy's will close for half a day so it's 12,000 employees can see the first showing."
Both the actual Macy's and Gimbel's department stores were approached by the producers for permission to have them depicted in the film. Both stores wanted to see the finished film first before they gave approval. If either store had refused, the film would have had to been extensively edited and reshot to eliminate the references. Fortunately at the test viewing, both businesses were pleased with the film and gave their permission.
The scenes at Macy's were shot on location at the main New York store on 34th Street itself. Shooting was complicated by the fact that the crew's power needs exceeded the store's electricity capacity and required additional power sources arranged in the store's basement.
"Lux Radio Theater" broadcast a 60 minute radio adaptation of the movie on December 20, 1948 with John Payne, Maureen O'Hara and Edmund Gwenn again reprising their film roles. The same studio broadcast another 60 minute adaptation, also with Gwenn, on December 21, 1954.
"Screen Director's Playhouse" broadcast a 30 minute radio adaptation of the movie on December 23, 1949 with Edmund Gwenn reprising his film role. The same studio broadcast a 60-minute version, also with Gwenn, on December 21, 1950.
The character of District Attorney Thomas Mara is clearly based on Thomas E. Dewey, a Manhattan District Attorney who went on to become the governor of New York and twice the (unsuccessful) Republican candidate for President (1944 and 1948). Jerome Cowan, the actor who played Mara, and Dewey bear a strong physical resemblance and both wore mustaches, highly unusual for professional men of the time. Also, the Judge mentions that the District Attorney is a Republican, also a rarity back then for elected officials in New York City.
According to Natalie Wood's biographer, during the shoot, the young actress was convinced that Edmund Gwenn was actually Santa Claus (by all accounts, Gwenn was a very good-natured man on the set). It wasn't until Wood saw him out of costume at the wrap party that she realized he wasn't Santa.
In the '70s Natalie Wood and Robert Wagner were approached about doing a TV remake of the film with Natalie's daughter Natasha Gregson Wagner as Susan. Wood turned it down because she'd been a child star herself and didn't want her very young daughter to start acting at such an early age.
The song that the little Dutch girl sings is "Sinterklaas Kapoentje, Leg wat in mijn schoentje, Leg wat in mijn laarsje, Dank je Sinterklaasje!" One translation is "Saint Nicolas Little Rascal, Put something in my little shoe, Put something in my little boot, Thank you little Saint Nicolas!"