Spock, and “Star Trek” in general, is a recurring theme on the nerd comedy. The cast has modified Rock-Paper-Scissors to the more complex Rock-Paper-Scissors-Lizard-Spock. Plus there have been past guest appearances from former Trekers including George Takei and Wil Wheaton.
As for what message Nimoy will relay to the brilliant Dr. Cooper, that’s unknown. But it’s sure likely that Sheldon will barely be able to contain himself following the interaction.