The most prominent characteristic of Spock is his logic nature making it difficult for him to understand human emotions and emotional behaviour. For further references see Spock on Wikipedia.
Since Sheldon with his extremely high intellect, his logic nature and his struggle to understand human emotions basically represents a modern version of Spock, this is understandable. However, it should be noted that Spock follows the "standard protocol of polite behaviour" much better than Sheldon does.
- When Penny gives Sheldon a napkin signed by Leonard Nimoy as a Christmas present, Sheldon is so moved that he believes no present he could give Penny would be of equal value and hugs her (0211).
- Sheldon obviously always chooses to be Spock in the game "Who am I?" and is very annoyed when the other guys immediately know who he is (0221).
- When the guys return from the expedition to the North Pole, Sheldon's beard looks the same as the one of "Mirror Spock" in the episode "Mirror Mirror" of Star Trek: The Original Series (0301).
- Sheldon has at least once met Leonard Nimoy in person and ever since owns a restraining order signed by Nimoy (0316).
- When the guys acquire a box full with "cool stuff" from a garage sale, Leonard finds a Spock action figurine. Well actually, he finds Spock's head with no body and Spock's body with Mister T's head. It is not clear who got to keep the figurine (0317).
Classic quotes from Spock are made by Sheldon in different episodes although it can only be speculated whether he does that because of his love for the character or because they were written for his role to highlight the similarity between Sheldon and Spock.
- In (0109) he answers Penny's question "How do you feel?" with "I don't understand the question.", which is the same Spock said to his mother in Star Trek IV: The Voyage Home.
Note: In the movie the answer highlights that Spock is supposed to be in control of his emotions and therefore unable to reflect and talk about them (0109).
- Sheldon frequently says "fascinating" when he discovers something interesting, which also is one of Spock's classic lines (0202).
- A reference to Spock's selfless sacrifice in "Star Trek II: The Wrath of Khan" is surprisingly sufficient to to convince Sheldon to join the Physics Bowl team although he had stated that he wouldn't use his "superior intellect" in a "tawdry competition" (0113).
Leonard: Do I have to quote Spock's dying words to you? "The needs of the many...
Howard: ...outweigh the needs of the few."
Sheldon: "Or the one." All right, I'll go.
Note: In the movie Spock saves the Enterprise by sacrificing himself and says to Captain Kirk that "The needs of the many...", [Kirk: "...outweigh the needs of the few."], to which Spock adds "Or the one." However spock's actual dying words are "I am and always will be your friend, live long and prosper."
- When Leonard dates Stephanie, Sheldon reveals that he has formed a "landing party" from his friends with him being Spock (0209, also see Star Trek References).
- Both, Leonard and Howard refer to Sheldon's excellent hearing with "damn his Vulcan hearing", a line that was frequently used by Kirk and Dr. McCoy referring to Spock (0301).
- When Howard and Raj try to convince Sheldon to come to a date, they remind him that even Spock had a date every seven years. Sheldon points out that Vulcan pon-farr is completely different from dating. "His blood boiled with mating lust" (0323).
See also Star Trek References.