Tom Selleck's memoir details top-secret Reno wedding, Princess Diana dance drama

"Magnum, P.I." star Tom Selleck pours out fond memories as thick as his famed mustache in "You Never Know: A Memoir" (Harper Collins, 339 pp., out now).

Selleck, 79, is working on his final "Blue Bloods" season. He writes about life lessons, his charmingly accidental Hollywood career, and the global superstar ride spurred on by his iconic 1980 "Magnum" role as the famed Hawaiian-shirt-loving private investigator.

"You Never Know" dishes nice, doesn't settle scores or talk politics, and the "Magnum"-heavy memoir doesn't dwell on Selleck's movies like 1987's "Three Men and a Baby" (or even discuss his long-running "Friends" role as Courteney Cox's much older boyfriend).

Here are Selleck's best "You Never Know" revelations.

Tom SelleckTalks 'Blue Bloods,' 'Magnum P.I.'

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Selleck won despite being a double 'Dating Game' loser

A University of Southern California basketball player and underachieving student, Selleck got his Hollywood start on the blind date competition show "The Dating Game." Selleck's first TV appearance, pitted against two other bachelors, was a disaster with nervously bumbled responses to the female contestants' flirty questions.

"I had lame answers, and I lost. I wasn’t funny. I didn’t enjoy it," he writes. The producers called for a return appearance. "For some bizarre reason, I went back. I was still terrified. I still wasn’t funny, and I lost again."

The double loss somehow turned into key career moves. Selleck got a Pepsi commercial and was noticed by a casting director.

Selleck tipped his fedora to Harrison Ford after losing Steven Spielberg's Indiana Jones role because of 'Magnum'

After shooting the promising "Magnum" pilot, Selleck was the unknown actor Steven Spielberg and George Lucas wanted to play Indiana Jones in 1981's "Raiders of the Lost Ark." Selleck wasn't allowed to see the script before his first high-pressure reading. But "the hat and leather jacket helped me understand the period," Selleck writes.

Reading along with actress Sean Young as Marion Ravenwood (that part went to Karen Allen), Selleck was called back for a second meeting.

“'We want you to play Indiana Jones.' I think it was Steven who told me," Selleck writes. "Look, I don’t have a clue how I responded. I hope at least I said 'Thank you.' This was a new franchise and they thought it needed a new face. I guess I was it."

But after "Magnum" was sold to CBS, the network president wouldn't release his star, fearing "that if he let me do 'Raiders,' I wouldn’t want to do 'Magnum,' and I would try and get out of it," Selleck writes. "I, of course, knew I would never do that."

Friends warned him not to watch "Raiders." Selleck bought a movie ticket and Jujyfruits. "Indiana Jones was Harrison Ford. The one errant thought that never entered my mind was 'That coulda been me,'" Selleck writes. "Somehow it didn’t bother me. It was such a good movie."

How much did Frank Sinatra bill for expenses for his six-day 'Magnum' shoot? It was still a bargain.

Frank Sinatra, a friend of "Magnum" star Larry Manetti (Rick Wright), had one condition about shooting a Season 7 guest appearance: "Just make sure I get to beat somebody up.”

The ailing Sinatra, then 70, committed to the part of an NYPD sergeant searching for the men who murdered his granddaughter. Even from his sickbed after being hospitalized for colitis, Sinatra assured: "Don't worry. I said I'll be there, I'll be there."

Sinatra's energy was limited in the shortened six-day shoot, making every moment count − especially for the final fight scene that Sinatra insisted on performing. Somehow a forbidden on-set camera flash ruined a key scene of a power Sinatra punch.

"Frank was not happy. We were not happy," Selleck says. "Our eyes landed on Larry, holding his Polaroid camera with a photo sticking out of it. 'I didn’t do it,' was Larry’s defense. The picture developed of Frank throwing a perfect punch."

The scene eventually worked. The landmark episode was the highest-rated "Magnum" in two years. It was a huge score even if production bosses were "shocked when they got the bill for Frank’s expenses," Selleck writes. "I don’t know the exact number, but it was in the six figures." Still a bargain.

A license flub nearly derailed Selleck's top-secret 'commando-like precision' Reno wedding

Selleck and his partner, British actress Jillie Mack, were intent on a secret family-only wedding. The clandestine event in Reno, Nevada, in August 1987, before shooting the final season of "Magnum," was a super-feat in paparazzi-fueled time. Mack hid her wedding dress in her handheld garment bag and Selleck flew in with only a carry-on to avoid suspicion. The star hid in the car as his father sized his wedding ring at a quickie Reno wedding store.

Selleck eventually had to exit his car and take off his sunglasses-and-baseball-hat disguise to identify himself to the shocked county clerk for the wedding license. But the operation to Reverend Dave's wedding chapel on the second floor of a strip mall was conducted with "commando-like precision." The "Magnum" fan organist was even ready with her surprise wedding music, taken from TV's nighttime soap opera "Dynasty."

"I didn't have the heart to tell her that 'Dynasty' was our Wednesday night competition," Selleck writes.

There was a major problem. A frantic search revealed the wedding license was left behind in the rush of leaving the clerk's office. "None of us knew what to say. We were stuck," Selleck writes.

Rev. Dave agreed to perform the wedding and pick up a new license himself as the family celebrated. The "Magnum" superstar's marriage to Mack was not reported until late the next month and has lasted 36 years.

"In Celebrityland, keeping our secret for a month might be a record," Selleck writes.

Selleck put his (left) foot down, refused to 'cut in' on John Travolta's dance with Princess Diana

John Travolta is a tough act to follow on the dance floor. So Selleck and Clint Eastwood steered clear as Travolta famously danced with Princess Diana at a White House state dinner thrown by President Ronald Reagan and Nancy Reagan in November 1985.

"We slipped away from all the dancers and moved to a spot slightly around the corner. By now John and Princess Di were dancing to an up-tempo number and rocking out. Everybody else stopped dancing and formed a circle around them, clapping their hands," Selleck writes. "Clint and I stood our ground."

A British woman urged action from the two stars as Travolta's second dance could "start rumors."

"Clint and I said nothing.'Mr. Selleck, you must step in and replace him.” Selleck recalls the women saying. “I’M NOT CUTTING IN ON JOHN TRAVOLTA!” was my reply, probably in too loud a voice. She was not pleased."

Selleck gallantly stepped in for a third dance, working his way through a thankfully slow song.

"Princess Diana was lovely, and there was a very shy quality about her in spite of her being well-schooled in the art of conversation," Selleck writes.