The book cover as shown says: "Art of Cookery by Brillat-Savarin." Jean Anselme Brillat-Savarin's book was titled "Physiologie du Gout" or "Physiology of Taste" and was not a cookbook at all, but a series of essays on the art of eating.
The recipe for Ortolans with plums, or Ortolans aux Questches, is really from Auguste Escoffier. Brillat-Savarin's book has no recipes.
On the train ride, Ace Conner produces his own truffles for his breakfast, but truffles would never be served whole, but shaved atop an omelet or diced to be included.
When Ricki, Ace and Bob walk into the little shop that rents them their costumes for Mardi Gras, they walk past an hourglass (that happens to be the same one used in "The Wizard of Oz"). Although there was no one else in the room, and the proprietor came downstairs apologizing that he had been upstairs watching the Mardi Gras, the sand in the hourglass is all in the top half.
When Ace and Ricki are on the waterfront in New Orleans and he is explaining Mardi Gras to her, the background behind them is moving and then suddenly changes directions.
When Ace Connors (John Hodiak) stops by to comment on the two ladies who are dining, he suggests adding saffron. This is a spice that can only be utilized at the beginning of a recipe as it needs to be macerated or infused into a liquid to release its flavors.
When Fly and Ricki arrive in the cab at the costume shop, she opens her door to get out. As she steps out, Fly is outside waiting for her. He didn't climb over her, nor would he have had time to exit from his side and run around to hers.
A moon phase and various dates and holidays are mentioned, and as such, to be correct, this film's story could only be taking place in 1943, yet there's nothing in the production to indicate a World War is happening. If it's meant to be 1946, then there are numerous factual errors, particularly with the dates involving Mardi Gras.
When Ricki and Ace get to El Paso, they cross into Mexico. While there, they take a stroll in the desert among the Joshua Trees. But Joshua Trees do not grow in Mexico. They grow in California, Nevada, Arizona, and the southwest corner of Utah.
When Ricki and Ace get to El Paso, they cross into Mexico and stroll through the desert among Joshua Trees and Saguaro cacti. But Saguaros only grow in the Sonoran Desert in Arizona and California, and the Mexican State of Sonora. It does NOT grow in Mexico as far east as Ciudad Juarez (across the river from El Paso).