According to the DVD commentary, Jane Fonda, Donald Sutherland and Martin Scorsese were offered the opportunity to voice themselves only for all three to decline.
After time is altered, the Ghost of Christmas Past pulls out a device to check what changed in the timeline. This is exactly what Al would do in the time travel TV show "Quantum Leap", and is likely an homage to that show.
Newspaper Headline: "EXCLUSIVE PHOTOS! Santa exits sleigh, flashes crotch"
The name of the Ghost of Christmas Past is Michelle. Lisa Kudrow played the title character of Michelle in Romy & Michelle's High School Reunion.
During season 1, Roger complains about having to be in hiding in the Smith house. However, he is seen in the 1970s talking to many people in his usual disguises and having jobs.