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.

Jackie Vernon, who voices Frosty, was known for his drab stand-up comedy acts and x-rated jokes.

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.

Jimmy Durante also recorded the song in 1950, but with slightly different lyrics.

Continuity

When Frosty attempts to count to 10, he starts counting to five on his fingers, and he has five fingers on one hand and four on the other. Then after he realizes he can only count to five correctly and chuckles, both hands have four.

When Hocus Pocus is telling Karen about the refrigerated boxcar, Karen's scarf is dangling on the ground. It is then back around her neck, and then on the ground again.

When Santa is threatening Professor Hinkle with no Christmas gifts unless he writes a sentence a zillion times, Karen is holding the hat, but when Hinkle runs off to do what Santa says, Karen not only no longer has the hat, it's nowhere in the scene.

Many times during the show, the petals of the flower on Frosty's hat switch from five to six and back between scenes.

The edges of Frosty's hat repeatedly switch from sharp to smooth and back many times during the show.



Factual errors

When the train heading for the North Pole stops to let another train cross, it stops

after

it has already crossed the track.



Revealing mistakes

When Karen is crying over the melted Frosty, her reflection doesn't move.

When Frosty says, "All right, come on now, what's the joke?" one of the boys before him is missing his feet.

Karen is cold despite the fact she is wearing earmuffs, a winter coat and boots. Yet Hinkle, who is wearing only a tuxedo, never seems affected by the cold.

When Karen is getting on the train with Frosty, one of her mittens becomes the same color as her skin for one frame.

When Professor Hinkle drops the eggs on the floor, one of them just disappears.



Miscellaneous

When Hinkle is chasing Frosty and Karen down the hill, he jumps up in the air and as he comes down, disappears.



Audio/visual unsynchronized

When building Frosty, two boys talk to Karen. One says "We're building a snowman, Karen", and the other says "You make the head". When they speak these lines, their mouths continue moving after they're done talking.

After the kids build the snowman, one of them suggests they name him Harold. Another kid responds with a strange sound (i.e. "Uh, Bruce?"). Obvious problem with the audio track.

As Frosty carries Karen into the greenhouse, his mouth never moves when he says, "Besides, I've been needing to take off a little weight, anyway."



Plot holes

Santa Claus brings Karen home safely, only to leave her alone on the roof of her house in the dead of night.



Character error

All the kids are wearing shorts out in the snow.

Professor Hinkle somehow manages to blow out a campfire with a single breath.

For some reason, Santa's sleigh is being pulled by only four reindeer.