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The 78-year-old actor, who first appeared in the sci-fi show last season, has agreed to return to the role of William Bell for at least two episodes.
Speaking to The Hollywood Reporter, he said: "The character was somewhat a blank slate and therefore attractive, because there is an opportunity to build an interesting and unpredictable character."
Nimoy - Spock in the original Star Trek series - went on to describe the character of William as "brilliant, wealthy and very powerful".
The sci-fi icon will next appear on Fringe in Thursday's episode at 9pm on Fox, and will feature in at least one more episode later this year. Discussions are reportedly underway for further appearances.
> Nimoy had 'delicious time' on 'Fringe'
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