During the Valentine's Day dinner, one of the guests asks Julia and Paul if they were spies in the war. Both of them deny this. At the time the modern half of the film was set (2002), the Childs' wartime files had not yet been declassified, but by the time the film itself was made (2009), their records had been made public and it was revealed that Julia had served as a top-secret researcher for the OSS. The filmmakers elected to go only with facts that were established knowledge in 2002, but the spy conversation was thrown in as a sly nod toward the later revelation.
Because of Meryl Streep's height (5'6") several camera/set/costume tricks had to be employed to mimic Julia Child's height (6'2"). Countertops were lowered, Streep wore extra high heels, and forced perspective camera angles were used.
Nora Ephron insisted that the actors and actresses not only ate for real but also fully played how tasty the dishes were.
In her research, Nora Ephron was very surprised to discover that Julia Child and Paul Child had a very intense sexual relationship - which they both wrote about enthusiastically to their friends.