The title refers to the possibility of a large asteroid hitting the planet and ejecting vast quantities of dust and ash into the atmosphere. This would significantly reduce the amount of sunlight reaching the earth's surface and cause a long global winter, resulting in failed harvests and famine. A large asteroid is theorized to have caused mass extinction amongst dinosaurs about 66 million years ago.
This is the first episode of the season to feature the entire main cast of the show.
A holiday episode, it takes place at Christmas time - though it is not the focus of the episode - Josh (Bradley Whitford) says "Feliz Navidad" and "Season's Greetings" and Leo (John Spencer) wishes the Vice President a "Merry Christmas"
This is the second time that C.J. uses tugging on the ear as a signal. Carol Burnett is famous for using the same signal to say "Hi" to her Grandmother.