Originally, June Foray voiced Karen, the Teacher, and the other children. Karen and most of the childrens' voices were replaced with those of actual children before the original broadcast. The end credits were never changed. In late 2017, some sources started listing Suzanne Davidson as the actor who provided the new voices. The original voices can still be heard however on the original MGM soundtrack, re-released years later by Rhino.
The special begins with children going to school on Christmas Eve, which was common up until the mid-60s.
While most Rankin/Bass specials are stop motion "Animagic", this was traditionally cel animated. The reason was because Rankin and Bass wanted it to have the feel of a Christmas card come to life. Cel animation also had techniques that were difficult to animate with stop motion, such as Frosty having to jump around.