Mark David Chapman killed John Lennon in 1980 to prevent the former Beatle from selling out. He's serving a life term at Attica.

"There was no emotion in my blood. There was no anger. There was nothing. It was dead silence in my brain. Dead, cold quiet, until he walked up. He looked at me. . . . he walked past me and then I heard in my head. It said, 'Do it, do it, do it,' over and over again."      - Mark David Chapman

Joni Leigh Penn sent at least a hundred letters to Cagney and Lacey's Sharon Gless over two years in the late '80s, including some with pictures of a gun. After the actress testified before the state legislature to encourage laws to make some records less accessible, the obsessed fan showed up at an unoccupied house owned by the actress. She had a rifle and held off police for seven hours before her surrender. She was sentenced to six years in prison.

Margaret Ray began to identify herself as David Letterman's wife in 1988. She broke into his Connecticut home at least eight times, once just days after her release from a nine-month prison stay on harassment charges. She was arrested for shoplifting in Connecticut last March and identified herself as a Secret Service agent, code name "Poobah."

Ralph Nau began stalking Olivia-Newton John in 1980, after he became convinced she loved him. Four years later, he tried to join her onstage at an L.A. concert (he was intercepted) and then followed her to Australia. Back in the United States later that year, he beat to death his autistic brother. Nau remains committed to an Illinois mental institution.

Michael Perry also fell for the winsome Australian singer's charms that year. Security consultant Gavin de Becker's people caught him on his way to her California house and encouraged him to leave the state. As soon as he got home to Louisiana, he killed his parents, his cousins and a baby nephew. He's currently on death row.

Arthur Jackson stabbed actress Theresa Saldana in 1982, in order that she would die, he would be executed and they would be reunited in heaven. He served 14 years and was released in June of this year. He was immediately extradited to England to face murder charges stemming from a 1966 robbery.

John Hinckley Jr. tried to assassinate President Ronald Reagan in 1981 to impress actress Jodie Foster. He now is confined to a Washington, D.C., mental hospital.