Among the celebrity gifts Whiteside receives is a mummy case from the "Khedive of Egypt." There was no Khedive of Egypt after 1914, when the Ottoman Empire joined the German alliance in World War I, and opponent Great Britain seized control of Egypt. The play on which the movie is based debuted in 1939, and references events of that 25-year-later period. It is just possible that the reference is to the last man to hold the title, who retired to Switzerland and died in 1944.
At one point in the film, Maggie Cutler goes to the window and comments on the snow falling outside. The falling snow is clearly visible outside the window. Then the camera goes to a medium shot, with all the windows visible, but from this angle, no snow is seen to be falling whatsoever.
There is a magical white pillow that alternately appears behind Whiteside's back as he sits in the wheelchair. It is most noticeable when Harriet Stanley, the odd lady, gives Whiteside a present which he does not open right away. It is there and it is not there pretty quickly. By the time Jimmy Durante (Banjo) visits him the pillow never returns.
Nurse Preen said to Mr. Whiteside, "If Florence Nightingale had ever nursed YOU, Mr. Whiteside, she would have married Jack the Ripper instead of founding the Red Cross!" While Florence Nightingale is indisputably an early leader of nursing, Henri Dunant founded what became the International Red Cross.
When Eleanor Roosevelt is heard on the telephone at the end of the movie, she is speaking with a British accent. She spoke with no such accent in real life, but rather spoke with a distinguished American accent.