When Frasier is listing several spoilers he mentions that Darth Vader is Luke Skywaler's father. This information was revealed in The Empire Strikes Back which featured John Ratzenberger as Major Derlin.
The container for donations for Carla is a actually a cheap plastic red vines tub.
The sounds of babies crying in the maternity ward are among the most commonly used foley effects for crying children, and has been used in a variety of films as well as music.
The title of this episode is a play on words, inspired by the Charles Dickens classic, A Tale of Two Cities. It was originally published in 1859.