Fran tells Mrs. Wentworth that her family's name was changed on Ellis Island and "now we don't know who the hell we were". However, the series establishes that Grandma Yetta came to the U.S. as a young adult, and thus would remember her original name even if it had been changed.
Much attention is given to the Wentworth family having come to America as Pilgrims, with both C.C. and Maureen Wentworth herself specifically mentioning her Wentworth ancestors on the Mayflower. However, she would have married into the Wentworth family, and thus would not be descended from the Mayflower Wentworths.
When C.C. enters the house and goes to place papers on a table, a cameraman can be seen stepping out from behind the doorframe behind her and back again.
When C.C first came to the house and put down a file on the front table, a staff in a red/pink shirt can be seen in the background. He/she tried to walk across the hallway but upon seeing the cast shooting, retreated back.
Niles and Mr. Sheffield spend part of their limited instruction time teaching Fran the details of setting the high table for a formal seated dinner. Afternoon tea does not incorporate any of the elements Fran is shown being taught, and is not served at the dining room table.