In fact, it's in "The Spock Resonance" that we first learn that Sheldon is planning on proposing to Amy, although the two are broken up at the time. This is revealed when he goes into his wall ...

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. In the season 5 episode, Sheldon and ...