Q. Where is Ken Olin of "thirtysomething" from? How old is he? Is he really married to Nancy on the show? Where can I write to him? - W.C., Madison Heights, Mich.

A. Olin was 36 on July 30. He was born in Chicago, raised in Highland Park, Ill. He was seen Tuesday (9-25) as Charles Stuart in the CBS movie "Good Night, Sweet Wife: A Murder in Boston," about the Charles Stuart murder case. Patricia Wettig, who plays Nancy, and Olin were married in 1983. Write: MGM/UA Television, 10202 W. Washington Blvd., Culver City, Calif. 90230.Q. How does the Fox network's "Fun House" for preteens come up with those wacky stunts?

A. Racing giant vacuum cleaners or coping with gallons of glop are among 600 stunts dreamed up by staff members each year. Only 250 stunts make it onto the air. "We hire kids to come in after school and try them out," reports host J.D. Roth, 22. "If they like one, it's on the show. If they don't, we call it a hairball. No go. . . . We just go to schools and hire them, or sometimes they're kids who want to be contestants on the show. . . . And they'll tell us what prizes they want - like maid service for a year for their bedrooms, helicopter lessons, limousine rides to school. . . ."

Q. Does David Crosby really intend to answer, on a national call-in TV show, all questions about his drug abuse?

A. Crosby already has taped a provocative exchange for the weekly series "The Inside Track with Graham Nash," which debuts next Sunday on the Arts & Entertainment cable network. On the show hosted by his musical pal, Crosby discusses his drug problems and subsequent 11-month jail stay on drug and weapons convictions, and guests in the audience also pitch him probing questions. Offstage, Crosby, Nash and Stephen Stills have patched up their sometimes volatile relationship and are planning another record (an acoustic album) by next spring.

Q. How old is Bruce Davison? Has he done any other movies than "Summer of My German Soldier" and "Poor Little Rich Girl"? - T.B., Marietta, Ga.

A. Davison is 44. He's been making movies since 1966's "Last Summer." Best known is the 1971 thriller "Willard" about a young man and his rats. (There may be a new flick, "The Return of Willard," in the future.) His most recent film in "Longtime Companion." Both "Soldier" and "Rich Girl" are among his TV credits.

Q. What has happened to Maggie McNamara, who was introduced in the 1953 movie "Three Coins in the Fountain"? My wife thinks it was really Audrey Hepburn, who changed her name from McNamara. - C.V.L., Scranton, Pa.

A. McNamara and Hepburn are two different people. McNamara was fashion model who turned actress. She starred on Broadway in "The Moon Is Blue" and made her movie debut in the film version in 1953. "Coins" was her second feature. She did only two more, "Prince of Players" in 1955 and "The Cardinal" in 1963. She did more theater work then disappeared from public view. In 1978, she was found dead of an overdose of sleeping pills. She was 50.

Q. We are fans of "In the Heat of the Night." Give us some information on that cute scene stealer Parker (David Hart). - K.B., LaGrange, Ill.

A. Hart was born in Marianna, Fla., and studied drama at Chipola Junior College there and at the University of West Florida in Pensacola. He made his professional debut playing Judd in a Florida production of "Oklahoma!" He did off-Broadway and stock before landing in TV guest roles. His feature films include "Legal Eagles," "Silver Bullet" and "Fandango." He's married, father of three.

Q. One of my favorite "Quantam Leap" episodes was repeated in August. The story was built around a stage play about Don Quixote. It looked as if the play was actually performed. Did Scott Bakula play the part when he was in the theater? - V.L., Newport, Ore.

A. Parts of "The Man of LaMancha" were staged for the TV show. Bakula's done many musicals, including "Romance/Romance," for which he had a 1988 Tony nomination, but he doesn't list "LaMancha."

A. I have a dinner riding on the answers to this: Who is Stephanie Zimbalist's mother? - S.W., Winnepeg, Manitoba, Canada.

A. Zimbalist is named for her mother, socialite Stephanie Spaulding, who married and divorced Efrem Zimbalist Jr. twice.

Q. How long did "Bonanza" run? What year did Pernell Roberts leave and what year did Dan Blocker pass away? - M.A.A., Royal Oak, Mich.

A. "Bonanza" was seen from 1959 to January 1973. Roberts, who was oldest brother Adam, left in 1965 and Blocker, who was Hoss, died in 1972. His loss and a new day and time contributed to the end of the show at mid-season.

Q. Give me the address of Arsenio Hall. - M.H., Youngstown, Ohio.

A. Paramount Televison, 5555 Melrose Ave., Los Angeles, Calif. 90038-3197.

Q. I enjoyed the new show "Top Cops." I have an uncle, dead now, I'd like to tell them about. What's the address? - A.S., Chesterfield, N.C.

A. "Cops" did well enough during its summer run to get a renewal for mid-season from CBS. Write Sonny Grosso/Larry Jacobson, executive producers, Grosso-Jacobson Productions, CBS-TV, 7800 Beverly Blvd., Los Angeles, Calif. 90036.

Q. Didn't Russ Tamblyn, the strange psychiatrist, and Richard Beymer, Benjamin Horne of "Twin Peaks," both star in "West Side Story" opposite Natalie Wood? - D.M.. N. Cape May, N.J.

A. They did. Although both did several other movies after the 1961 musical drama, by 1964 both had dropped out of the limelight for other pursuits. Beymer became a top-flight cinematogrpaher and film editor before returning to acting in 1983 in the feature film "Cross Country." Tamblyn concentrated on art and poetry but did some stage and TV work.

Q. I say some years back there was a TV program, like the old "Ed Sullivan Show," called "Major Bowls." My son laughs at me and says there was Ed Sullivan and Ted Mack but no show ever by the name of "Major Bowls." Who's right? - M.W., Chesapeake, Va.

A. Years ago, starting in 1934, Major Edward Bowes created and hosted the "Original Amateur Hour" on radio. (One radio amateur who made it big was Frank Sinatra.) After Bowes death in 1946, his associate Ted Mack took over the "Amateur Hour" format and brought the show to TV in 1948. It lasted until 1960. Incidentally, Sullivan never used amateurs. His guests were all professionals, although some were little known before he gave them a TV break. A closer parallel to the "Amateur Hour" was "Arthur Godfrey's Talent Scouts" which gave exposure to aspiring professionals with little experience.

Q. Settle a bet for us. Al says Angela of "Who's the Boss" is nearly 45. Sandy's betting 35. - J.M., East Detroit, Mich.

A. Judith Light, who plays Angela, was 40 last Feb. 9.

Q. Would Sally Field and Burt Reynolds ever team up again for a movie?

A. Actually, Reynolds said "thanks but no thanks" to an invitation to team up with his old flame Field in a movie being produced by her husband, Alan Reisman. It's not that he fears bad blood on the set; he's just too busy with his CBS series, "Evening Shade." Suddenly, everyone's asking for Reynolds, who hasn't been sought out in a long time. "That's why," he muses, "people don't quit this business."

Q. Does Roy Rogers ever record nowadays?

A. Rogers just cut a new version of his old TV theme song, "Happy Trails," with Randy Travis for Travis' "Heroes & Friends" album, and the two teamed up for The Nashville Network special "Randy Travis - Happy Trails," to air Oct. 17. Rogers, a founding member of the Sons of the Pioneers, also is working on a new RCA record titled "Tribute."