Bing Crosby & David Bowie - Little Drummer Boy / Peace on Earth
Ella Fitzgerald & Louis Jordan - Baby It’s Cold Outside (or it's multitude of renditions done the same year, or since -- although the song is not really about Christmas)
well this is from the movie 'TOYS' starring Robin Williams---The Closing Of The Year/Happy Workers to hear a sample of it go to amazon.com it is a good song and does go into a duet at on point in the song