Despite the fact that this television film was produced and first broadcast in 1977, "It Happened One Christmas" carries a 1978 copyright date (in Roman numerals) in the closing credits.
When the townspeople sing "Auld Lang Syne" in the Bailey/Hatch house, there is no attempt made to sync the song with their lip movements.
When Mary is about to jump off the bridge during the blizzard, you cannot see her breath.