Dr. Quinn tells Mrs. Marley that no one could have known that Mr. Marley has a bad heart. If future episodes, Dr. Quinn consistently knew when a patient had a bad heart.
When Dr. Mike first holds the book of A Christmas Carol in her hands, the sound of a modern telephone ringing can clearly be heard in the background. The same ringing happens at the beginning of a later segment fading in from commercial.
Dr. Quinn devoted her teen-aged years and her twenties to study and learn to be a doctor. It is illogical for her to regret actually achieving her only goal.
Dr. Quinn wears her hair in a casual style when she goes to the Christmas Eve party. She is from an elite family of Boston. She would have worn her her up.