From Nookipedia, the Animal Crossing wiki
Jack (パンプキング, Panpukingu, Pumpking), self-proclaimed Czar of Halloween, is a character from the Animal Crossing series whose species is unknown. He appears twice a year, first on October 1st (in (Animal Crossing: New Leaf), and then for Halloween from 6:00 PM until 1:00 AM the following day. He distributes spooky furniture, which can only be obtained through him. He wears a pumpkin on his head which, during Halloween, makes him indistinguishable from other villagers in the town who will also ask for candy. Jack, like all other holiday-related characters, was absent from Animal Crossing: Wild World, as was Halloween and candy.
In Animal Crossing
In Animal Crossing, he will be somewhere in town during Halloween. Unlike the other villagers, who wear the same clothing as him, he will not chase you. This is the same for Tortimer, who on the night will give the player a model of Katrina's tent. Upon talking to Jack, he will give the player an item of spooky furniture in exchange for candy. Doing this throughout the event will complete the set.
Jack returns in City Folk with Halloween and candy. He was announced on the Japanese website for City Folk, along with other characters. His role remains the same as in Animal Crossing, and he now calls himself the Czar of Halloween. He sends a letter out to players earlier in the month, warning of his arrival, and telling them to have candy ready. Nook's store starts selling candy on the 1st of October.
In New Leaf Jack can be found walking around the player's town on October 1st to October 7th (however he will disappear the day after the player speaks to him) where he will tell them about Halloween and what will happen on that night. During this time, the player cannot work at The Roost. On Halloween, Jack can be told apart from the other villagers by his darker orange pumpkin mask and the carving on it. When given a piece of candy he will then ask the player if they want their choice of a mask or piece of furniture from the Spooky Series.
Jack appears in Happy Home Designer when his amiibo card is scanned into the game via the amiibo phone, and will ask the player to build a house for him. Like all Special Characters, he will leave the theme up to the player, and won't request for certain furniture to definitely be in his house.
When visiting Jack's RV at the campground, the bottom screen will display the following:
Jack gives a piece of furniture every time the player gives him Candy. All the furniture pieces look like pumpkins or Jack O'Lanterns. They are orange and, like all holiday-exclusive furniture sets, score very highly with the Happy Room Academy.
Items obtained by approaching Jack without having any candy are arguably considered part of the Spooky Series, but are actually not. These items include:
Jack appears as a collectible trophy.
Names in other languages