Guest star George Eads went on to star in CSI: Crime Scene Investigation (2000). Two of his co-stars in that show have had recurring roles on ER (1994) - Marg Helgenberger in Season 2, and Jorja Fox in Seasons 3 to 5.
The title is a line from the Christmas song "Do You Hear What I Hear?" written by Noel Regney (lyrics) and Gloria Shayne Baker (music) as a plea for peace during the Cuban Missile Crisis (1962). The song was originally recorded by the Harry Simeone Chorale, but it was Bing Crosby's recording (1963) that was the most popular and is still played at Christmas time today (2009).
Paul McCrane [Robert Romano] and George Eads [Paramedic Greg Powell] both appeared in the same CSI episode: World's End.