BackstoryEditThe Pumpkinator was created when the irresponsible 10 year old "Timmy Turner" used his Fairy God Parents to wish that every costume on halloween was real. This transformed four of his classmates into the components of a doomsday weapon known as the Pumpkinator.
Timmy was narrowly able to unwish the wish and send the Pumpkinator to a small island in the Bermuda triangle known as Un-Wish island. It's unknown how the Pumpkinator came to Halloween Town, perhaps because of his overall halloween theme.
Either way he would come to work for Oogie Boogie.
Oogie summond his minion to deal with Mini Mandy after she came to rescue her brother Grim Jr. Oogie ordered the Pumpkinator to kill Mini and it promptly chopped her up. Mini gave her right eye to her older brother thereby giving him all her Nergal powers. Jr promptly ripped the Pumpkinator apart with his new powers.
After the Angel took Mini away Jr.'s powers interpreted his body as "weak" and decided to give him a new one in the form of the Pumpkinator causing him to go out on a out of control rampage absorbing the souls of most of Halloween Town and some of Mandy's armies. The ghost known as "Clock Work" summoned the ghost known as Dark Danny to contain the rampage of the beast.
This gave Clock Work the distraction he needed to enter the Pumpkinator's body to retreive Jr.s soul and send it to rescue his sister in the first of the Nine Rings of Heck. Jr. and Mini's souls were brought back to Halloween town where they were able to take control of the weakened Nergal Reaper body.