William Shatner is standing in a mostly bare rehearsal room in Hollywood, his arms outstretched as he recites the closing lines to his Broadway-bound one-man show. Naturally, the subject of the moment is his career — that strange, constantly mutating accumulation of TV series, movies, guest spots, online projects, commercials and more.

“It’s easy to say no,” he says, addressing an invisible audience. “Saying yes carries more danger to it. Saying yes is risky business — but how much richer my life has been because of it.”

If there is one inviolable law of the Shatnerverse, it is simply that: Say yes. Shatner’s career is defined by a bottomless capacity to try it all. Nothing is too weird or outlandish; selling out is nothing to be ashamed of. His oddball career choices form the backbone of “Shatner’s World: We Just Live in It,” which opens Thursday in New York at the Music Box Theater for a two-and-a-half week run before he launches a national tour at the Pantages Theatre on March 10.
 

The show marks Shatner’s return to Broadway after 50 years — his last Broadway appearance was in the 1961 comedy “A Shot in the Dark,” opposite Julie Harris and Walter Matthau. The danger of having said “yes” to the new show is clearly weighing on him during the recent L.A. rehearsal period. “Every time you’re in something, you wonder if it’s any good,” he says during a lunch break. “Until it’s in front of the public, and they’ll tell you. So that moment of trepidation is with you all of the time… It never goes away.”

“Trepidation” is a word that Shatner used often during the interview. As hard as it is to believe today, Capt. James T. Kirk of the USS Enterprise was once a struggling New York stage actor with a resume consisting primarily of Shakespeare and stock theater in his native Canada. (He once understudied Christopher Plummer in “Henry V” at the Stratford Festival.)

“I was making $35 a week, and I was a big success as far as I was concerned,” says Shatner, talking about his early New York days. “I didn’t know anything else. I was following some intuition. I come from a very practical family. The idea of becoming an actor was so foreign.”

“Shatner’s World” toggles warp speed between various high points in his life and career, and some low points as well. (The show inevitably covers some of the same ground as Shatner’s 2008 memoir “Up Till Now.”) The production requires Shatner, 80, to be on stage for close to 100 minutes without intermission. For those who think he’s too old to be doing this, Shatner has thought up an ingenious audience hook.

“I was joking with somebody saying that people should come to the theater to see me because I may die on stage,” he says with a big laugh. “I’m at the age where people are dying. So they can say that maybe he’ll die and we’ll see him dying.”

The ability to mock oneself isn’t common in Hollywood, but Shatner possesses it in abundance. His lack of self-importance — no doubt a source of his everlasting appeal to his fans — includes a willingness to discuss his professional failures, of which there have been more than a few.

Shatner recalls appearing in Mart Crowley’s “Remote Asylum” at its world premiere at the Ahmanson Theatre in 1970. The play began with Shatner and an actress coming on stage in a darkened theater. The actor recalls: “As we’re coming out in front, she says to me, ‘Do you think we’re in a disaster?’ And the curtain goes up. And that resonated for the rest of the evening. It turns out we were!” (The play was poorly received and closed out of town.)

A more recent disappointment was the CBS sitcom “$#*! My Dad Says,” based on the popular book and Twitter feed. The series was canceled last year after less than one season. Shatner said the show should have been a hit.
 

“Shatner’s World” devotes ample time to the actor’s TV successes in”Star Trek,” “T.J. Hooker” and his late-career resurgence in”Boston Legal,”for which he won an Emmy Award. The script is adapted from his stage show “Kirk, Crane and Beyond: William Shatner Live,” which recently toured Australia, New Zealand and Canada, and featured the actor in conversation with a moderator about his life and career.

The new show dispenses with the moderator and condenses material. “We’re taking what he had done previously and tightening it,” says Scott Faris, the show’s director. Rehearsals have been short by Broadway standards, with just a couple of weeks in Hollywood and a week or so in New York followed by two days of previews.

The idea for the Broadway transfer and national tour came from producers who caught the earlier stage show touring Canada. They approached Shatner and his manager about doing a U.S. tour, and then later decided that a limited Broadway run would serve as a launch.

Much of the show’s commercial potential lies in Shatner’s appeal to multiple age groups, says Seth Keyes, a producer and vice president at Innovation Arts & Entertainment, a live-entertainment company. “He runs the gamut, from hip, younger audiences, to a slightly older demographic of ‘Boston Legal’ fans to the ‘Star Trek’ generation,” he says.

“Shatner’s World” could be classified in the theatrical mini-genre known as the serio-comic celebrity autobiography. Recent practitioners, including Carrie Fisher and Joan Rivers, have mixed career autopsy with hilarious and sometimes gruesome personal anecdotes to create a self-aware exercise in stage therapy.
 

In Shatner’s case, the personal can sometimes be painful. The show touches on the death of his wife, Nerine, who drowned in 1999 in the couple’s swimming pool at their Studio City home. The show also discusses divorce — the actor has been down the aisle four times — and the difficulties that come with raising three children.

But the overall tone is light and hopeful. At the end of the show, Shatner even performs a song from his album “Has Been.”

One of the show’s key moments offers an origin myth of Shatner’s idiosyncratic and widely imitated vocal delivery. The actor was working on the Broadway play “The World of Suzie Wong” in 1958. “It was very poorly received in the beginning. It should have closed but we didn’t because we had this big advance,” Shatner recalls.

In the process of willing people to stay in their seats, the actor says he started delivering his lines faster, with oddly placed pauses. Audiences found it funny. A serious drama about a man who falls in love with a prostitute in Hong Kong became a comedy and ran for more than 500 performances.

After the national tour of “Shatner’s World,” the actor says he will participate in a couple of horse shows (a personal passion) and tape episodes for the Discovery Channel series “Weird or What?” that he hosts.

“Retire? To what?” Shatner says laughing as he resumes rehearsals.

– David Ng