The Jack-O-Lanterns ( also known as the Pumpkinheads, although their real species name is not known) were a group of shape-shifting extraterrestrials that were residing on Earth - integrating themselves into human society using their shape-shifting ability to appear human while taking on human names.
The aliens had a variety of abilities - including been able to 'create' various items including large amounts of candy and even an entire street that they could live in, which was hidden away from humans. In their Jack-O-Lantern forms, they were shown as been able to talk even with their pumpkin heads removed (speaking with hissing voices), spew fire out of the pumpkins and move at rapid speed.
They were also carnivores, with them eating only meat. This included humans, although they would only consume fat people. Two of their members - Shane and Shana, who were twins - had become best friends with a human girl called Drew (living next door to her before they moved away) and shared their secret of been aliens. Neither of the two revealed their carnivorous nature until later.
The Jack-O-Lanterns appeared in the 48th Goosebumps Book Attack of the Jack-O'-Lanterns, which was later adapted into an episode of the Goosebumps TV Series. A Jack-O-Lantern also appeared in the 2015 Goosebumps movie - been part of the army of monsters from the Goosebumps universe brought out into the real world by Slappy the Dummy.
Shane and Shana plan with Drew to get back at Tabitha and Lee - a pair of bullies who have ruined Drew's last two Halloweens. The first was Lee's Halloween party, where he and Tabitha pretended to be a pair of burglars. The second was when Drew prepared a Halloween party, but Tabitha and Lee didn't go - staying at Lee's cousins instead.
The plan consists of Drew, Walker, Shane and Shana meeting up with Tabitha and Lee and the group of them going trick-or-treating together - during which Drew and her friends will prank them. Although Drew's mother is reluctant to let her daughter go out trick or treating as a result of four people going missing from a nearby town, her father lets her as she will be in a group and not on her own. Shane and Shana reveal the prank to their own people, who agree to help them.
Meeting up with Tabitha and Lee and waiting for Shane and Shana to show up, the group were surprised by a pair of Jack-O-Lanterns. Although Tabitha and Lee immediately thought it was both Shane and Shana, they appeared to change their minds when the pumpkinheads began to spew flames. Following the pumpkinheads, they were led into a street they had never seen before - with the people giving out a lot of candy. As the night draws on and the children try to leave, the Jack-O-Lanterns refuse to let them go and state they want the children to 'Trick-or-Treat forever'. Not scared, Tabitha and Lee pull off the pumpkinheads - only to be shocked when they find no head underneath and the pumpkinhead in their hands still talking. When they try to run, the two Jack-O-Lanterns encircle them rapidly - preventing them from escaping.
When the children's bags get full as the hours trick-or-treating continue, the Jack-O-Lanterns demand they eat the candy already in their bags, getting impatient when the children take a long time - especially when the children complain of getting tummy ache as a result of eating the candy. As the Jack-O-Lanterns head back towards the street they and the kids were previously, everyone in the houses step outside and are revealed to be Jack-O-Lanterns, who encircle them and claim that the children will all be changed into Jack-O-Lanterns. Tabitha and Lee run away screaming after two pumpkins are shoved on their heads.
At this point, the Jack-O-Lanterns drop their disguises, with the two who had been with the children revealed to be Shane and Shana. Drew happily states that it's great to have aliens as friends, with Shane and Shana's people disappearing into the sky. When Drew asks what Shane and Shana eat since they don't eat candy, the twins revealed they were carnivores that ate obese humans - telling Drew not to worry as she is not an adult and is not plump enough yet. Drew - shocked at what she has heard - questions the twins as to whether or not they are joking.
In the TV version, there are some differences to the book:
In the book, the Jack-O'-Lanterns tell the kids to start eating their candy when their trick-or-treat bags get full. In the TV episode, the Jack-O'-Lanterns simply tell the kids to dump their candy onto the pavement.In the TV episode, the two Jack-O'-Lanterns are shown as been able to shoot an energy beam out of their claw hands and tell both Tabitha and Lee that they are going to change them into Jack-O'-Lanterns by putting their pumkinheads on top of Tabitha and Lee's heads - to which Tabitha and Lee run away screaming. This differs from in the book, with Tabitha and Lee running away after seeing everyone in the street they were trick-or-treating down previously changed into Jack-O'-Lanterns - who then encircle them before trying to put the pumpkinheads on them.
The final difference between the book and the TV version is that after the prank and Drew asks what Shane and Shana eat, the two reveal their carnivorous nature and make the intention that they plan to eat Drew when she's an adult and is plump enough. In the TV episode, Shane and Shana reveal their true alien forms to Drew and Walker, as well as warning Drew not to eat all the candy she has collected as she may get fat (revealing they ate the four fat people who disappeared earlier) and they will be back next Halloween - before both Shane and Shana get aboard a spaceship and fly off.