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"The Prestidigitation Approximation" is the eighteenth episode of the fourth season of the American sitcom The Big Bang Theory. This episode first aired on Thursday, March 10, 2011.[1]


Priya feels threatened by Leonard hanging out with his ex-girlfriend Penny all the time and tells Leonard that he has to cut the cord with her. Meanwhile, Sheldon attempts to figure out Howard's magic trick.

Extended Plot[]


Priya and Leonard.


Priya asks, "How many Star Trek uniforms do you have?"


Good-bye, Leonard.

Leonard and Priya are in bed together at Leonard's place. They discuss the racism implied in Leonard's attempt in trying out positions from the Kama Sutra and, shortly after, Priya urges him to get contact lenses as she claims he has beautiful eyes.

Later, at the cafeteria, Howard offers to show Raj a magic trick, but Sheldon intervenes and tells him he shouldn't be wasting his time with such trivial matters. Howard performs the trick, which involves him knowing which card Raj pulls randomly from the deck, anyway and impresses both Raj and Sheldon. Although Sheldon mocks the trick, he is still keen to unravel it. Leonard comes in with his new contact lenses which are clearly incompatible with him, and he crashes into several people and furniture.

Back at apartment 4A, Howard impresses Penny with his magic trick as Sheldon watches carefully, apparently still stumped by the card trick. Leonard comes back from shopping for "more grown-up" clothes with Priya and they head for his room. Priya voices her feelings about Leonard hanging out with Penny all the time and asks him to terminate their relationship, and he reluctantly agrees. Meanwhile, Howard continually impresses his friends with the magic trick, and Sheldon's ego is further crushed when Howard confirms that Penny successfully figured it out.

Leonard and Penny bump into each other in the laundry room, where Penny "saves" Leonard's new silk shirt that he was about to ruin by throwing it into the washing machine. She goes on to compliment Leonard's choice in Priya as a real winner, but concludes with an ambiguous "there are a lot of bitches out there."

Penny gathers her laundry and looks at Leonard for a moment before saying goodbye, but Leonard stops her and nervously tries to hint that he would like to see her less without saying it directly. His obscure method of "cutting their ties" confuses Penny, and she leaves the room thinking no differently of their friendship. Later, when Priya questions him about whether or not he spoke to Penny about this issue yet, he hastily confirms that he has, hoping that the issue is now settled.

Meanwhile, Sheldon has grown increasingly obsessive with understanding Howard's magic trick, and has even gone as far as hacking into the Oak Ridge National Laboratory's Cray supercomputer to analyze shuffling patterns and looks into procuring Uranium-235 off of Craigslist after wondering if Howard used a radioactive tracer.


Penny spots Priya and Leonard in the Tandoori Palace.

Later that evening, Priya and Leonard are having dinner at the Tandoori Palace and Priya reveals that her company has offered her a job in Los Angeles. Leonard is thrilled at this news, but as the couple hold hands they're interrupted by a tapping noise and look up to see Penny smiling and waving at them through the window. She then enters the restaurant and makes a scene, mocking Leonard's clothes and appearance before picking food off his plate and drinking out of his glass. These actions anger Priya, who deduces that Leonard never fulfilled his promise to cut his ties with Penny.

At the cafeteria, Sheldon claims he has solved and improved Howard's magic trick. Howard and Raj are interested to see his version of the trick, but soon see that he has barcoded all the cards and used a scanner (which Sheldon claims is a wand) to identify it and send a message to his phone. Howard criticizes Sheldon's execution was pathetic, and Sheldon is once again annoyed, because he assumed they weren't smart enough to figure it out. Howard shows the trick again, but this time it is revealed to the audience that there is no trick, as Raj (and Penny) has been playing along with Howard's wild guesses as a mean joke on Sheldon, knowing that he would go nuts trying to figure it out.

Later, Leonard finally musters up the courage to tell the truth to Penny, and it quickly dawns on her that there are complications in their friendship due to Leonard's current relationship with Priya, and she agrees to keep a distance. She kisses him and tells him goodbye. Leonard goes after her, but runs into the door frame because of his contact lenses.

Sheldon is depressed that he is unable to solve the magic trick. The Department of Homeland Security busted him for hacking into the Cray supercomputer and trying to buy Uranium-235 over the internet (rather than arresting him, the DHS let his mother deal with him, which Sheldon claims is a far worse punishment.) Howard offers to show it again. However, this time Sheldon requests Howard try it on him, and Howard reluctantly agrees. Sheldon isn't "gullible" like Raj is, and with his finely-tuned senses, he will spot Howard's trick as soon as Howard screws up. With all of his focus on Howard, Sheldon doesn't notice Raj signaling to Howard that Sheldon's card is the two of hearts. Furiously, Sheldon storms out of the cafeteria as Raj and Howard dissolve into laughter.



  • The TV Critic: "The card trick plot was fantastic. It was far from the funniest story you will see but for a show that so often tells incomplete stories it was very refreshing to see one written so perfectly...Unfortunately everything that Leonard did made him look like a coward. The fact that he can't bring himself to be honest with Penny does him no favors. He then lies to Priya and pathetically hopes things will work themselves out. Then when Penny does him a favor by figuring out what is really going on and taking it well he almost comes on to her...I don't think the producers of The Big Bang Theory are intentionally making Leonard so un-admirable. But regardless that is what's happening and it makes the show less fun to watch. Otherwise this was pretty good."[2]
  • The A.V. Club gave this episode a B-.[3]
  • IMDb user reviews


  • Title Reference: A "prestidigitation" is another word for magic tricks or tricks of illusion, and an 'approximation' is a guess or estimate; this title is a reference to how Sheldon tries to figure out how Howard performed his magic trick.
  • Chuck Lorre's vanity card.
  • This episode was watched by 12.06 million people with a rating of 3.8 (adults 18–49).[4]
  • This episode aired in Canada on March 10, 2011, with million 3.132 viewers and a weekly ranking of #1.[5]
  • In the United Kingdom, this episode aired on August 4, 2011, with 1.316 million total viewers and a weekly ranking of #11.[6]
  • Episode transcript [1]

Costume Notes[]

  • Sheldon wears a grey and yellow striped shirt, a grey and purple striped shirt, and his light blue Penrose triangles t-shirt.



Analyzing shuffling techniques, Sheldon attempts to figure out Howard's card trick combination-wise.

  • Bernadette and Amy do not get featured in this episode (whether mention, on-screen appearance, speaking role or background cameo) because Melissa Rauch and Mayim Bialik do not get credited to appear as main cast members in this episode and they are not included in any of the story lines throughout this episode.
  • Leonard tried to use contact lenses in the 7th grade.
  • Leonard was his school's debate club president.
  • Leonard has two Star Trek uniforms, everyday and dress. One appears to be a beige wraparound tunic and the other a green-gold shirt, both command division colors. In "The White Asparagus Triangulation" (S2E9), Sheldon refers to Leonard as Captain Kirk in his "landing party". Raj has a Lieutenant Uhura uniform, which Priya and her family are embarrassed to know. Leonard asks, "Hypothetically, if I had access to a Lieutenant Uhura uniform, would you wear it?" She finally wears the uniform for Leonard in "The Roommate Transmogrification" (S4E24). 
  • Leonard can hear Penny's toilet flush from his apartment.
  • First time we see the Tandoori Palace which has been referenced in previous episodes. Leonard apologizes to Priya for bringing her to an Indian restaurant to which she replies she likes Indian food. Leonard says "Or as you probably call it back home, food". This line may have been take from Friends (1994) - S01E24 - "The One Where Rachel Finds Out", when Joey says to Ross: "Move on. Go to China. Eat Chinese food" when Chandler chirps in: "Of course there they just call it food".
  • Sheldon's board displays the number of ways (52! or approx. 8 x 1067) to shuffle a deck of playing cards.
  • While Penny whispers to Howard, Sheldon should have heard what they were saying due to his "Vulcan Ears".
  • Raj's birthday is October 6.
  • A poster for neutrinos is visible in the cafeteria.
  • This is not the first time that Sheldon has been busted by the government. In "The Luminous Fish Effect" (S1E4), Sheldon's mom said that, as a boy, Sheldon tried to build a nuclear reactor in the barn, but was foiled when two men from the government showed up and told him that his project was illegal.
  • Howard is not always doing the same card trick each time he demonstrates it.
  • Penny bids a sad farewell to Leonard, beginning a story arc for most of the rest of the season where she tries to avoid hanging out with him for Priya's sake.
  • Despite always being depicted as wearing boxer shorts in all his underwear scenes, this episode is the one and only time Leonard is mentioned to wear briefs. (mentioned by Sheldon during the infrared camera scene)
  • Third episode where Leonard bumps into a piece of apartment architecture due to a lack of foresight after season 1's "The Big Bran Hypothesis" (S1E2) and "The Pancake Batter Anomaly" (S1E11)


Penny: (to Howard) Y'know, I think I know how you did the card trick.
Sheldon: Oh, please. If I don't know, you don't know. That's axiomatic.
Penny: C'mere. (whispers in Howard's ear)
Howard: You're right.
Penny: Not too bad for someone who doesn't know what "axiomatic" means.
Sheldon: Drat.

Sheldon: Howard, if I may interject here with a piece of friendly advice. Is working on magic tricks really how you want to spend your time? Granted, you’re just an engineer, but that doesn't mean you might not someday build a geegaw or a thingamabob that may get you a thank you in someone else’s Nobel Prize acceptance speech.

Penny: Oh, for god’s sake, Leonard, this is about Priya, isn't it? She doesn't want me hanging out with you.
Leonard: Yes. There, I said it.
Penny: Okay, look, I happen to like your girlfriend.
Leonard: And she likes you.
Penny: No, she doesn't.
Leonard: Not really, no.
Penny: It doesn't matter. Look, I promise from now on I will keep my distance from you.
Leonard: Well, now, hold on. What kind of distance are we talking about? Because we are neighbors. I mean, I can hear the toilet flush in your apartment.
Penny: You can hear my toilet flush?
Leonard: I don’t listen for it, but it’s nice to know everything’s okay with your plumbing. The building’s plumbing.
Penny: Leonard, I get it. You’re in a new relationship now. And I’m happy for you. So why don’t we just shake hands and part friends?
Leonard: Well, now hold on, how about this? How about we still hang out, but on the down-low?
Penny: Are you really that kind of guy?
Leonard: No. I actually felt kinda silly just saying on the down-low.
Penny: (sadly) Good-bye, Leonard.

Howard: (about Sheldon trying to figure out his magic card trick) You ever notice when he thinks real hard, it smells like bacon?