"Star Trek" actor Leonard Nimoy died at the age of 83 Friday.
Best known for popularizing the character of Spock, Nimoy has made countless cameos reprising the character, including on CBS' hit comedy "The Big Bang Theory."
Perhaps his best appearance on the series was a voiceover cameo in which he gave Sheldon (Jim Parsons) advice in the form of a tiny Spock action figure.
CBS screenshot
In the season 5 episode, Sheldon and Leonard (Johnny Galecki) both receive collectible "Star Trek" figurines from their neighbor Penny (Kaley Cuoco).
In a dream sequence, Spock convinces Sheldon he should open and play with his mint-in-the-box "Star Trek" toy.
CBS screenshot
After Sheldon breaks the toy, he switches it with Leonard's, thinking he won't notice.
Spock returns in a later dream to weigh on Sheldon's conscience for switching the toys.
Watch the two dream sequences clipped together below: