Jack spends much of his time growing pumpkins to replace his old heads, which eventually spoil and need to be replaced. In the fifth Oz book The Road to Oz (1909), Jack has settled in a large pumpkin-shaped house near the Tin Woodman's castle in Winkie Country. Jack notes that he no longer has a father. By the end of the second Oz book, Tip, who was originally born Ozma, is changed back into a female by the same magic that made him male. To remedy this, Tip created the Sawhorse to serve as Jack's mode of transportation. It will take me a little time to discover whether I am very wise or very foolish.'ДЄlthough Jack Pumpkinhead would not get tired from walking, his joints would still wear out. 'For although I feel that I know a tremendous lot, I am not yet aware how much there is in the world to find out about. For example, after bringing Jack to life, Mombi has the following exchange with him: Even Mombi was not without a curious interest in the man her magic had brought to life for, after staring at him intently, she presently asked: 'What do you know?' 'Well, that is hard to tell,' replied Jack. However he manages to come up with random bits of wisdom and common sense often. Jack is not known for his intelligence which seems to depend on the quality and number of the seeds in his pumpkin-head at that time. Instead, she decided to test her new Powder of Life on him. When Mombi saw Jack, she almost smashed him to pieces. From Mombi's chest he took some old clothes for Jack purple trousers, a red shirt, a pink vest with white polka dots, and stockings, to which he added a pair of his shoes. Jack was made by a little boy named Tip to scare his guardian, an old witch named Mombi. He has a large carved jack-o'-lantern for a head which is where he gets his name (unlike most jack-o'-lanterns, the seeds and other pumpkin guts were not removed so it substitutes for his brain).

Jack's incredibly tall and skinny figure is made from tree limbs and jointed with wooden pegs.

Jack first appeared as a main character in the second Oz book by Baum The Marvelous Land of Oz (1904).

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