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"The Thespian Catalyst" is the fourteenth episode of the fourth season of the American sitcom The Big Bang Theory. This episode first aired on Thursday, February 3, 2011.[1]


Sheldon gets a lot of negative responses about his physics lecture. After talking to Amy, he decides to take acting lessons from Penny because he believes it will help him entertain his audience. Meanwhile, Raj, who is without a girlfriend, is having daydreams romantically involving Bernadette.

Extended Plot[]


Sheldon lecturing - Kill me now!

Tbbt howard injury

Howard; after getting hit by a truck.


Raj's fantasy about Bernadette.

Sheldon gives a lecture making his usual condescending comments. Meanwhile, the gang is enjoying the tweets of the people that attended Sheldon's lecture; all negative towards him from Twitter. When he arrives home, he expects the reaction to his lecture to be monumentally positive, but his friends proceed to read out some of the tweets.

Later, at the Cheesecake Factory, Raj mentions how it's sad to "accidentally walk into a gay bar and have no one hit on you." This statement makes Leonard and Howard think Raj's deprivation of female company has caused some issues. Bernadette comforts and reassures Raj.


Penny breaks Sheldon.

Amy tries to cheer Sheldon up, but on failing that she proposes he take acting lessons as it is the responsibility of the teacher to "communicate as well as entertain and engage." Sheldon goes to Penny to ask for acting lessons; she agrees after he offers to pay her. Sheldon's first acting class in improvisation ends up stressing Penny, and in the second, they act out a script that Sheldon wrote based upon a fan fiction story when he was ten years old; "Where No Sheldon Has Gone Before." Penny takes the role of Mr. Spock, saying Sheldon needs to be out of his comfort zone so Sheldon plays his mother who is sending him off to the 23rd century at the request of Mr. Spock, who says that he is the best hope to bring peace to a vast and troubled galaxy. Eventually the script brings out very emotional feelings from Sheldon. He cries because in the play he doesn't want to get taken away. Penny calls his mother to help him settle down: "Hi, Mrs Cooper. It's Penny. Yeah, I think I broke your son". Then she has Sheldon talk to his mother, who begs her not to let Spock take him to the future.

Raj has a daydream in which Howard has been offered a fellowship, but he has to leave the country and while he is away requests that Raj satisfies Bernadette's sexual needs; Raj willingly agrees to it. Later he daydreams that Howard is hit by a truck and is not going to make it, but is able to convey his last wish, which is for Raj to take care of Bernadette sexually; again he agrees. The final dream sees Bernadette approaches him infuriated, but the scene quickly changes into a Bollywood-style dance routine proclaiming their love to each other. Snapping out of each of these, Raj eventually comes to the conclusion that he is definitely not gay.



  • The TV Critic: "This is exactly what you would expect from the show: two good story ideas which go nowhere. The writers are far more interested in creating jokes around their initial concepts than actually bringing them to a conclusion. I think the show suffers because the best jokes come out of fully realized stories."[2]
  • The A.V. Club gives this episode a B.[3]
  • IMDb user reviews


  • Title Reference: "Thespian" in "The Thespian Catalyst" refers to Sheldon's decision to take acting lessons. Thespian means actor. It is named after Thespis |Thespis of Icaria, the "Father of Greek Tragedy". He was a poet who lived during the 6th century B.C.
  • Chuck Lorre's vanity card.
  • This episode was watched by 13.83 million people with a rating of 4.3 (adults 18–49).[4]
  • This episode aired in Canada on February 3, 2011, with 3.192 million viewers and a weekly ranking of #3.[5]
  • In the United Kingdom, this episode aired on July 7, 2011, with 1.062 million total viewers and a weekly ranking of #12.[6]
  • Episode transcript [1]

Costume Notes[]

Sheldon prime

73 Prime

  • Leonard wears his Ames Brothers "Wisdom" shirt. and his periodic table shirt.
  • Sheldon wears his "73 Prime" t-shirt


  • Howard says, "FYI, I think that’s what Darth Vader said just before he started building the Death Star." In the Legends continuity, Darth Vader did build the Death Star, as explicitly revealed in The Rise and Fall of Darth Vader: Of all the operations that Darth Vader oversaw, the most important was the construction of the Death Star, a moon-sized battle station that, when finished, would be equipped with a super-ray capable of destroying entire planets.
  • Penny does not appear in the Cheesecake Factory scenes.
  • The was originally named the Sci-Fi channel, and Leonard cannot get used to the change.
  • Raj considers Labradoodles to have high sex appeal.
  • The shirt Sheldon wears when asking Penny for acting assistance displays the number 73, which Sheldon declared as the best number, in "The Alien Parasite Hypothesis".
  • Sheldon serves as a guest lecturer on the topic of topological insulators.
  • Penny has Mary Cooper's phone number memorized or has it on speed dial.
  • Raj's hallucination with Bernadette turns into an Indian music video.
  • Penny's acting skills are seen for the first time.
  • In "The Work Song Nanocluster", Sheldon says that Penny has a "don't knock on my door before eleven o'clock or I punch you in the throat" rule; however, in this episode, Penny requests that he come over at 9AM for his acting lesson.


(Penny calls Mrs. Cooper)
Penny: Hi, Mrs. Cooper. It's Penny. Yeah, I think I broke your son. Okay, hold on. (hands the phone to Sheldon) Talk to your mother.
Sheldon: Mommy, I love you, don't let Spock take me to the future.

(The ending scene at Caltech cafeteria where the infuriated Bernadette enters Raj's table looking very cross)
Bernadette: (she shouts at Raj crossly) Okay, Raj, I know you’ve been avoiding me and Howard, and I’m not leaving until you tell me what’s going on inside that little head of yours.

Bollywood Dance Number Lyrics:
Raj: Like the wild elephant, I am trumpeting my love for you,
Bernadette: Like a hidden flower, my sweet fragrance comes into view,
Raj: My heart burns for you like a sun at noon.
Bernadette: My desert welcomes you like the rain in monsoon.
Raj: You are my heart.
Bernadette: My universe.
Raj: You are my heart.
Bernadette: My universe.
Both: My universe.
Both: You are my heart, my universe (x3)
Both: My universe...

Sheldon: Now, in this pivotal scene, Sheldon's mother, played by you, argues with an emissary of the United Federation of Planets, Mr. Spock, the role I will bring to life.
Penny: Okay, that's fine, but let's try and get you out of the comfort zone.
Sheldon: Why would we want to do that? It's called the comfort zone for a reason.
Penny: Okay, the whole point of this is to loosen you up a little, so I'm thinking you'll play the role of your mother, and I will bring the life to Mr. Spock.
Sheldon: I'm sorry, you'll be Spock?
Penny: It's only logical.

Sheldon: Oh, tweets about my lecture. Hmm. That's rather unfair. That's downright cruel. Plus, insects has six legs. Yeah, I'm not familiar with the acronym KMN.
Leonard: Oh, uh, from the context, we think it means 'kill me now'.
Sheldon: Well, I suppose everyone's entitled to their own opinion. I think I'll turn in. (walks into the bedroom hall then turns around) I didn't want to teach those poopy heads, anyway! (Goes into his room)
Howard: FYI, I think that's what Darth Vader said just before he started building the Death Star.

Penny: Hi. Welcome to Pasadena Shoes. I'm Penny. How may I help you.
Sheldon: I'll have a frozen yogurt.
Penny: Well luckily, we also sell yogurt too. Read the sign.
Sheldon: Oh yes, it says Camarillo State Mental Hospital. That is the only explanation why you would be selling shoes and frozen yogurt.

Leonard: I'm still not adjusted to how the SyFy channel spells their name now. S-Y-F-Y. That's siffy.
Raj: Uh-huh.