"Platoon" Oscar-winning writer-director Oliver Stone was in demand last night at two special showings of his hot new film, "Wall Street," starring Michael Douglas, Charlie Sheen and Daryl Hannah. One was a high-powered dinner screening at the Motion Picture Association of America for some of the people responsible for regulating Wall Street. The other showing, sponsored by the Center for National Policy, included a reception on Capitol Hill with a showing at the Avalon Theatre.

Scheduled to attend the MPAA show were all five members of the Securities and Exchange Commission -- Chairman David Ruder, Joseph Grundfest, Edward Fleischman, Charles Cox and Aulana Peters -- as well as Rep. Edward Markey, chairman of the telecommunications and finance subcommittee of the House Energy and Commerce Committee. Among the senators expected were William Armstrong, Max Baucus, Ernest Hollings, Howard Metzenbaum and William Cohen. Ken Lipper, a former New York investment broker writing the novelization of Stone's movie, was scheduled for the Center for National Policy showing and reception, which Sens. Bill Bradley, Pat Moynihan and Alan Cranston were expected to attend. Out and About That unseen person whom Mikhail Gorbachev paused to shake hands with Tuesday night as he and President Reagan walked the red-carpeted hallway between the White House East Room and State Dining Room was a member of the Marine Corps orchestra. The orchestra was playing John Philip Sousa's "Hands Across the Sea" following the treaty signing ceremony, and Gunnery Sgt. Celeste Blase smiled as the Soviet leader looked her way. He extended his hand to the violinist, who was standing behind a pillar, as millions watched on television. Blase, who stopped playing to shake hands with Gorbachev, said yesterday that in her eight years with the band she has often witnessed history, but Tuesday she felt she had participated in a small way ...

Hospital Report: Sen. Quentin Burdick is expected to be released today from St. Luke's Hospital in Fargo, N.D., where he had been recovering from a fall on ice Monday. The 79-year-old Democrat was admitted to the hospital with a possible concussion. A staff spokesman said Burdick would be flying back to Washington immediately ...

Actor Paul Newman, in town Tuesday for the Gorbachev meeting at the Soviet Embassy, was seen in New York yesterday with his left hand and arm in a cast. He had undergone surgery for an undisclosed ailment. When reporters attempted to get more details, Newman's publicist Fran Curtis said he told her: "Tell them {reporters} to pursue matters of greater consequence" ...

Veteran United Press International reporter Helen Thomas wasn't at her usual post at the White House yesterday. She was submitting to a charity roast conducted by her former UPI colleague Al Spivak at the Shoreham Hotel. It was part of the Christmas Roast of the Saints and Sinners, and Spivak, public affairs director for General Dynamics, said that in Thomas' 27 years at the White House "she made the enemies list long before Dick Nixon even invented it." Then he said that through the years, "presidents have thought of Helen as a cross between Lucrezia Borgia and Typhoid Mary. But Helen thinks of herself as Mother Teresa. Then again, she thinks of Sam Donaldson as Albert Schweitzer" ...