Marc Jacobs will be doing his Halloween costume ball in Provincetown, Mass., this year. The designer, in talks to take over Dior, is underwriting a lavish Beaux Arts Ball at the Town Hall tomorrow. It was such a hot ticket that all 900 of them sold out in minutes, frustrating some locals. The event is even being masterminded by Chelsea Clinton’s wedding planner, Bryan Rafanelli. We can’t wait to see what Jacobs will wear — but he was seen shopping for sequined bras at Patricia Field’s store this week.