Plaster Mountain Theme Park

Plaster Mountain is an amusement park in Springfield. Its main attraction is a giant mountain made of plaster at the center of the park.

Dwight David Diddlehopper was abandoned by his mther at the park when he was a baby. He took Marge hostage to the park, asking her to give him the day his mother didn't: to have fun, ride with him on some rides, etc. In exchange, he'd let her go.