Pumpkin Heads are monsters from the Goosebumps book, Attack of the Jack O' Lanterns.
The Pumpkin Heads are creatures who have jack-o'-lanterns for heads and breathe out fire. This was the disguise of a race of shapeshifting aliens.
Drew, Walker, Tabby, and Lee head out, they run into two people dressed in costumes with pumpkinheads. Tabby and Lee are convinced that the two are Shane and Shana. The two pumpkin-headed people take the kids to a street that the kids are sure was never there before, saying they will get lots and lots of candy from the incredibly generous inhabitants. But when it starts to get late, Drew and the others learn that the two pumpkin headed kids will not let them go home, and want them to trick-or-treat forever. Tabby and Lee are still not scared, so they try to take the jack-o'-lanterns off the two, but when they do, they find that there is no head beneath them and that the jack-o’-lanterns are still talking.
As the hours drag on and the children's bags become full, the two Pumpkin Heads force the kids to eat the candy they already have to make room in their bags (Tabby and Lee have pillowcases). The Pumpkin Heads get impatient and order them to eat faster, leading Tabby to accidentally smear chocolate in her hair. The children then complain that they are painfully full, but the Pumpkin Heads continue to demand that they eat every piece that they were given. After they make some room in their bags, the Pumpkin Heads get the children moving again. They lead to a street inhabited with Pumpkin Heads. Soon, Drew, Walker, Tabby and Lee are surrounded by Pumpkin Heads. Four Pumpkin Heads (including the two that brought the children where they are) walk towards the group with four craved pumpkins. They tell the children they're shall become Pumpkin Heads when put the pumpkins over their heads. After they successfully put pumpkins over Tabby and Lee's heads, Tabby and Lee run away, leaving Drew and Walker.
At this point, the two Pumpkin Heads reveal that they are Shane and Shana and that the entire ordeal was merely the prank that the four had created to scare Tabby and Lee. It turns out that Shane and Shana are actually aliens with the strange abilities like shape-shifting and the other people in the neighborhood are their brothers and sisters who were in on the prank as well. As Shane and Shana prepare to depart, Drew offers them some candy, but the two tell her that their people eat human flesh. They state that she needn't worry yet, she's not an adult yet. Besides, they squeeze Drew's arm to feel how chubby she is and state that she's not plump enough yet.
One of The Pumpkin Heads appear in the Goosebumps film as one of the many monsters released by Slappy the Dummy, although it doesn't appear that much in the movie, it appears on the theatrical poster.