When Leonard Nimoy's guest role on CBS's The Big Bang Theory was announced a few weeks back, it was made very clear that he would not appear on screen, but would offer his voice as Spock in some fashion.
With the episode, dubbed "The Transporter Malfunction," airing this week, more information has been revealed. First off, you can see Jim Parsons and Nimoy together in the above set photo, which debuted on TVLine. But, more importantly, CBS has started running commercials for the episode that show exactly how Nimoy's voice will appear: through the body of a Spock action figure in Sheldon's dream sequence.
It looks to be one of the Diamond Select Toys Star Trek Retro Cloth Spock figures, which take their cues from the 1970s Mego line. It seems like an appropriately geeky way to bring in an all-time genre icon into the series without having the man himself on screen.