Sneak peek: Nimoy reminds Sheldon of his human half on 'Big Bang'

"Big Bang Theory" star Jim Parsons, left, and guest star Leonard Nimoy of "Star Trek" fame. Monty Brinton / CBS

"The Big Bang Theory" features its most logical guest star Thursday when the CBS comedy welcomes Leonard Nimoy.

During the episode, the icon voices a Spock action figure that Leonard (Johnny Galecki) gifts to his roommate and encourages the highly illogical Sheldon (Jim Parsons) to embrace his "human" form and play with a valuable mint-in-box Star Trek transporter toy.

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But what could persuade the anal retentive collector in Sheldon to open the box and destroy the toy's value? In a clip from Thursday's "The Transporter Malfunction" episode exclusive to The Hollywood Reporter, Nimoy's "little Spock" uses logic and reason to help convince Sheldon to live a little using phrases like "illogical" and "fascinating."

"I thoroughly enjoyed myself," the "Star Trek" legend told The Hollywood Reporter of his experience filming the episode. "[They're] a talented company and a smart show; they made me welcome."

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Co-creator Chuck Lorre told THR at "Big Bang's 100th episode party last year that the episode in which Penny (Kaley Cuoco) gives Sheldon a Nimoy-signed napkin -- complete with his DNA -- stands as his favorite "nerd moment" on the long-running series.

“[Sheldon] was so overcome with affection for her, he physically hugged her, which he can’t do as a character," he said at the time. "We all stood there on the stage and everybody got all fablungent and weepy. It was a moment that rose above the show and became something else.”

Check out the clip to see just who says "Set phasers to dumb."

"The Big Bang Theory" airs Thursdays at 8 p.m. on CBS.

Which is your favorite "Big Bang" moment? Will Nimoy's appearance be at or near the top of your list? Share your thoughts on our Facebook page!

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