Jack Frost is the anthropomorphic personification who wanders around at night drawing ferns on the windows (in Hogfather, and possibly afterward, he expanded his repertoire somewhat, after a chance meeting with the Verruca Gnome). He is a thin figure with icicles for hair and a nose, if the drawing by Paul Kidby is anything to go by. He apparently never sleeps,as was his response when the Verruca Gnome suggested that he "must go through an awful lot of bedsheets". From this, we can determine that he is spiky all over. He had fleeting roles in Reaper Man and Hogfather. It is undetermined how, if at all, Jack Frost and his work are connected to the Wintersmith.
- Note: He also draws paisley patterns. They may look like fern patterns, but there's a difference.
On Roundworld, Jack Frost is an elfish creature who personifies crisp, cold, winter weather; a variant of Father Winter (AKA Old Man Winter). He is a figure some believe to have originated in Viking folklore.
He is said to leave frosty crystal patterns on windows on cold mornings. Those who believe in Viking folklore roots state that the English derived the name Jack Frost from the Norse character names, Jokul ("icicle") and Frosti ("frost"). Another theory is that he is a much more recent import into Anglo-Saxon culture from a Russian fairy tale. In the Finnish epos Kalevala Canto number 30, translated from Finnish into English by Keith Bosley, Jack Frost is the son of Blast, "Pakkanen Puhurin Poika". Other tales in Russia represent frost as Father Frost, a smith who binds water and earth together with heavy chains. In Germany however, it is an old woman who causes it to snow by shaking white feathers out of her bed.
Weirdly, Jack Frost didn't appear in the film Hogfather but David Jason (Albert) had already played a character of that name.