The cook speaks Cantonese, a dialect from the Southern part of China. The other Chinese actors in the movie speak Mandarin.
The Japanese soldiers throughout the film are wearing the wrong helmets.
When the aircraft attack the fictional town of Tsiensin while Gladys is outside in the fields, an explosion erupts from a still pond. There was no splash from the presumed bomb.
The aircraft which attack the fictional town of Tsiensin while Gladys is outside in the fields are painted white with an orange disk on the side in the style of Japanese military aircraft of the period. But the aircraft are actually Airspeed AS.10 Oxford trainers, built and flown in Britain. They were never supplied to Japan.
As the children come marching into town at the end of the movie singing "This Old Man", their singing voices have a distinctly British accent although all the children are native Chinese.
The captain is talking with Gladys and says that someone will listen to anything for an extra bowl of rice. The story takes place in northern China and rice is only eaten in southern China. Noodles made from wheat was the mainstay of the Chinese diet in the north. Later in the film it appears Gladys takes a serving of rice from a large pot, and lastly on the journey with the children they come across some uncooked rice which Gladys picks it up.
Eagle eyed viewers will see many plants in this film which are not commonly found growing wild in China. The location was partly chosen, because Portmeirion had certain Chinese plants growing near it, such as rhododendrons.
The character of Gladys Aylward is supposed to be British, but she speaks with a slight Swedish accent. Also while the real Aylward was short and quite homely, Bergman is noticeably tall and beautiful. The real Gladys had a Cockney accent and labored in the working class as a maid.
The film makers, since release, have been criticized for casting Ingrid Bergman, a tall woman with a Swedish accent, as Gladys Aylward, who was in fact short and had a cockney accent.
The Chinese gave Gladys the name Ai-weh-deh, Chinese for Virtuous One, not Jan-Ai as used in the movie.