A jack-o'-lantern is a carved pumpkin associated with the holiday Halloween. To make one, the top is cut off and the insides scooped out. A face or picture is carved into the side, a lit candle is placed inside, and the top replaced. The light then flickers giving an eerie effect.
The Bleecker Street Carnival had a Jack-o'-Lantern contest for Halloween. They lined the finalists on a table for all to see and lit them. The first place winner was a particularly gruesome winner.
Green Goblin even had some pumpkin bombs that would go off like fireworks and produce a Jack-o'-Lantern design.