As John Winchester grew up in moved to Lawrence, Kansas, he described himself as "a mechanic from a family of mechanics." It may be assumed that Millie either remarried, or that there were mechanics on his mother's side. Alternatively, he went to live with relatives or was fostered or adopted.
- Writer Adam Glass had intended to introduce Millie, with actress Louise Fletcher being his choice to play the character. However, he was unable to figure out the right take to bring the character to life.
- A photo of Henry, John and Millie can be seen on Lady Antonia Bevell's cork board detailing the Winchester's lives.