Jack Frost is the personification of frost and cold weather, a variant of Old Man Winter held responsible for frosty weather, for nipping the nose and toes in such weather, coloring the foliage in autumn, and leaving fernlike patterns on cold windows in winter. Starting in early 20th century literature, more filled-out characterizations of Jack Frost have made him into a sprite-like character. He sometimes appears as a sinister mischief maker. Jack Frost is a sprite and the personification of crisp, cold, winter weather, a variant of Old Man Winter. He is also at times shown as a mischief-making spirit, carefree and happiest when he can do his own thing. With no obligations, he is able to flourish. He is traditionally thought to leave the frosty, fernlike patterns on windows on cold winter mornings (window frost or fern frost) and nipping the extremities in cold weather. He is sometimes described or depicted with paint brush and bucket coloring the autumnal foliage red, yellow, purple, and orange. Jack Frost is friendly but if provoked, he will kill his victims by covering them with snow. On the other hand, some versions depict him as a kinder being who only wishes to enjoy himself and bring happiness to others. He is often portrayed as an older man, though other depictions show him as a young adult or a teenager. Jack Frost is a being of imagination; as an immortal spirit of frost, he symbolizes the youthful nature and wonder of those who play in the snow and the frost.