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After casting the actor to play his iconic Spock in the new big-screen space adventure, Trek's brain trust found a character for him — scientist-mogul William Bell — on the supernatural TV show they created: Fringe (Fox, season finale Tuesday, 9 p.m. ET/PT).

Nimoy, 78, hadn't played Spock in nearly 20 years when Trek director J.J. Abrams and writers Roberto Orci and Alex Kurtzman asked him to put on the pointy ears again.

"I thought these people really had an appreciation of what we did in the original series and films," Nimoy says. "They had an appreciation of the Spock character, who I felt had been somewhat neglected for some time. In fact, in the last film that Bill Shatner (Captain Kirk) did, along with the rest of the original crew, Spock wasn't even included."

(Asked about Shatner's initial complaint about not appearing in the new film, Nimoy says: "He's been very good about it. He called and said, 'Now we're even.' ")

Orci says Spock serves as "the connecting tissue" to the original Trek, which spawned multiple series and films over four decades.

"What a fascinating thing to see a character played out over 43 years," he says.

The elder Spock's actions are tied to the threat facing the younger Spock (Heroes' Zachary Quinto) and Kirk (Chris Pine). The half-Vulcan, half-human, who has scenes with Spock and Kirk, offers nods to Trek lore.

Nimoy, the only original cast member in the film, says he is flattered that the Spock role is continuing with look-alike Quinto.

"We talked about the struggle ... to find the balance between the emotional and the logical," Nimoy says. "We talked about how the makeup evolved. It took some time to find the shape of the ears, the color of the skin, the haircut, the eyebrows."

Recently, Abrams called again to ask if Nimoy would like to play Fringe's mysterious Bell. Nimoy signed on as the pivotal character for three episodes. "At least," Orci says.

Bell — "a mix of Howard Hughes and Bill Gates," according to Orci — is the founder of corporate giant Massive Dynamic and a former colleague of mad scientist Walter Bishop (John Noble). Like Spock, he is a genius, but he may use logic as a weapon, Orci says.

Nimoy asks: "Is he mischievous? Negative? Positive? Is he going to save the world or destroy it? What is he trying to do?"

Nimoy's scene Tuesday is with Anna Torv, who plays FBI agent Olivia Dunham. "There is an interesting character touch in the scene with Olivia that I hope audiences will enjoy, a slight idiosyncratic moment," he says.

Nimoy, who has turned his creative energy toward photography, would consider another outing in the role he made famous.

"I can't ever say never again," he says. "Star Trek and Spock have gone through a lot of resurrections," including series cancellation, a decade gap before the first movie and the character's death in the second film.

After Spock died, "I thought, 'Well, that takes care of that.' And it certainly didn't."