The Iran-contra hearings have been a hot ticket. People have stood in line to be part of the scene being played out on Capitol Hill, even though the best seat in town is in front of the television set at home. A number of celebrities, in town for a variety of reasons, have used whatever connections they have to find a way to sit in.

Singer John Denver had called to request a seat at yesterday's session, but canceled just before it began. Some of the other stars seen in the room over the past few weeks have included Morgan Fairchild, Ellen Burstyn, Shelley Duvall, Kirk Douglas, Judd Nelson, Joe Piscopo and Lloyd Bridges. And, not surprisingly, none other than political satirist Mark Russell. With all that free material being tossed about, Russell couldn't afford not to be there taking notes.

Denver's Capitol Hill Day

John Denver didn't show up for the Iran-contra hearings because he was having problems of his own elsewhere on Capitol Hill. He was in town to bring attention to the problems of farmers and said he was angry that he was stood up by two senators. Sens. Tom Harkin (D-Iowa) and Kent Conrad (D-N.D.) didn't appear with Denver at a scheduled news conference because they were attending a memorial service for Secretary of Commerce Malcolm Baldrige, who was killed last weekend while practicing for a rodeo.

Denver told reporters outside the Capitol that "not only has our government turned their backs on us in the farm crisis, but they will not allow us to do a news conference in the Capitol." The news conference was moved outside because there is a rule barring such events in the Capitol unless a member of Congress is present.

Volcker's Farewell

President and Nancy Reagan headed an impressive list of economists, bankers and political leaders who came out Tuesday evening for Secretary of State George Shultz's party for retiring Federal Reserve Board Chairman Paul A. Volcker, who spent eight years as head of the nation's powerful central bank.

Among the guests at the private dinner were Alan Greenspan, Volcker's replacement as chairman at the Federal Reserve; former secretaries of state William Rogers and Alexander Haig; former secretaries of the treasury William Simon and Donald Regan, who was also White House chief of staff; banker David Rockefeller; and publishing tycoon Malcolm Forbes. Out and About

The legendary Oscar-winning director John Huston is in serious but stable condition at Charlton Memorial Hospital in Fall River, Mass., where he was taken after an emphysema attack on his way to film his role in a new movie, "Mr. North." Huston, who will be 81 next week, has had heart disease and emphysema for years and uses an oxygen system. The movie, directed by his 25-year-old son Danny, also stars his Oscar-winning daughter, Anjelica. It is based on the novel "Theophilus North" by Thornton Wilder, a jazz-age comedy set in Newport, R.I. Because of his illness, Huston immediately decided to remove himself from the film and is to be replaced by Robert Mitchum, who was flying in from California yesterday to join the cast, which also includes Lauren Bacall and Burgess Meredith ...

Former first lady Rosalynn Carter says her daughter Amy was not dismissed from Brown University for poor grades. "She did not flunk out," she said yesterday in Charlotte, N.C., where Jimmy Carter and his daughter are helping to build homes for the poor. "She just didn't finish. She's burned out," her mother explained. She said Amy, a sophomore, was an A student and a National Merit finalist who had no problem with grades. Both of her parents support what they say was Amy's decision to drop out. "I think it was good for Amy to take the year off," Rosalynn Carter said. "During the last semester she got so immersed in apartheid and peace efforts that she didn't feel like she was ready to make a final decision about her career" ...

Buckingham Palace can say what it wants, but it does seem strange that Prince Charles and Princess Diana were at separate engagements yesterday -- their sixth wedding anniversary -- hundreds of miles apart. That should give London's tabloid press something to titter about. The Palace spokesman snorted: "It happens to a lot of people. They happen to be apart today, but they will be meeting up tomorrow in Cornwall, when the princess joins Prince Charles there" ...