Man who didn’t get to Hell or Heaven.
He outsmarted the Devil thrice in his life. He conjured and used crosses and whatnot to trap the old bugger, only letting him go if the Devil promised to never take his soul. The Devil promised.
But Jack didn’t get to Heaven either, since he had been a no-gooder. The Devil couldn’t take him since he had so promised, but being a “good sport” he carved a turnip (Jack’s fav food) hollow, and put a candle inside so Jack could have a light-source with him when wandering the world. Forever.
The Ghostbusters version of the story is identical to the original folktales except that the reader is shown the present day happenings as well. Jack asks for help from the Ghostbusters so he can find peace.