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"The Loobenfeld Decay" is the tenth episode of the first season of the American sitcom The Big Bang Theory. This episode first aired on Monday, March 24, 2008.


Leonard hears Penny singing poorly. When she asks them to come to a performance, showcase Leonard lies and says that he and Sheldon have plans. Sheldon is uncomfortable with the lie which Leonard gives and so he comes up with a new complicated one.

Extended Plot[]


Would you like to see me sing?

The episode opens with Sheldon and Leonard arriving home and arguing about "Terminators". They are debating the rationale of SkyNet's use of terminators; Sheldon grilling Leonard on why SkyNet would need to create a petite, hot, 17 year old killer robot, since artificial intelligence does not have teen fetishes. They suddenly hear terrible singing from the upper floors, they soon discover it was Penny, who announces that she has landed the role of Mimi in the musical show; "Rent". Although it is apparent that the boys are bringing home takeout food to consume, Leonard lies to Penny that they were just taking out some trash; forcing Sheldon to put the bag of takeout food in the trashcan in the lobby. As if one good lie deserves another, Leonard fibs that he and Sheldon will be attending a Symposium on Molecular Positronium given by Dr. Emil Farman-Farmaian to avoid attending Penny's show and hurting her feelings. When Penny leaves, Sheldon is deeply disturbed by how easy Leonard was able to lie convincingly, noting that this is a quality of sociopaths.

Sheldon wakes Leonard up in the middle of the night because he is concerned that Leonard's lie is full of holes and is easily seen through. He is concerned that Penny might go online to get information about the seminar they said they were attending, and then they'd be caught in the lie. Leonard tries to explain the social procotol that led him to lie to spare Penny's feelings.

The next morning, Sheldon confesses to Penny that Leonard lied about the symposium. He fills Leonard in, informing him that he has created a new, better lie; one where Penny will not be able to uncover evidence to bust them: he told her that Leonard was lying to protect Sheldon, because Sheldon was embarrassed that they were going to be participating in a drug intervention for Sheldon's cousin, Leo, in Long Beach. He tries to get Leonard to understand how important little details are in keeping the lie alive, believable, and "un-unravel-able". Sheldon has gone so far as to create a Facebook page for Leo, an online blog, and a listing on, all of which will confirm Leo's issues and act as confirmation of their story. He was able to make Leonard part of the alibi for non-attendance by setting the fake intervention in Long Beach, as Sheldon doesn't drive, and would need Leonard to thus go along with him. All they have to do is leave the apartment Friday and return in the wee hours. Then they can claim that Leo went to rehab, AND, they will have set the stage to use Leo as a diversion for any other future things that they might want to get out of attending. Leonard is concerned that there is no way he'll be able to remember all of these details, and Sheldon proudly announces that he doesn't have to. He told Penny that Leonard was embarrassed about Leopold, and so Penny has already agreed to play along with the original lie.

The Loobenfeld Decay image

Penny comforting Sheldon's "cousin".

On the day of her show, Penny stops by at apartment 4A to see Leonard and Sheldon before their intervention for "Leopold" at Long Beach, she acts as if they were attending the symposium. Upon hearing that Howard and Raj were been left out of the symposium, Howard starts getting angry. Penny then asks Sheldon to reveal that they are not going to the symposium, but rather an intervention, Penny then leaves for her show. After Penny leaves, Sheldon and Leonard tell Howard and Raj about the lie. After a discussion, they decide to go to Long Beach (where they were supposed to travel for the intervention) to see the RMS Queen Mary. Later that night, Sheldon confronts a cranky Leonard (because he was awakened in the middle of the night) about the lie, he tells Leonard that there is a slight flaw based upon the personality and motivation of his fictional cousin.

As Leonard is in no condition to talk, Sheldon decides to discuss the matter in the morning. The next morning, Leonard discovers a man eating cereal in his apartment, when questioned the man answered he was Sheldon's cousin "Leopold". Sheldon later clarified that the man was Toby Loobenfeld, a research assistant at the university but he also minored in acting, which is why Sheldon enrolled his help to act as his drug addicted cousin. Penny comes by to check how the intervention went, Sheldon tells her he has failed to convince "Leopold" to go to rehabilitation, but was successful in getting him back to the apartment. Penny is introduced to "Leopold", but soon it turned into an ugly fight as he and Sheldon disagree on the characteristics that Toby portrays. Penny then invites Leonard over to see a recording of her performance, he reluctantly agrees. Soon, "Leopold" begins to bond closely with Penny which disturbs Leonard.



  • "The focus on one story gives the episode a clear structure and a memorable identity. It is both funny and plausible, but is not a classic episode of comedy. The humor just isn't strong enough to match the clever story." - The TV Critic's Review
  • IMDb user reviews.


  • Title Reference: Toby Loobenfeld is a research assistant who was cast to play Sheldon's drug addicted cousin.
  • Chuck Lorre's vanity card [1]
  • This episode was watched by 8.63 million people with a rating of 3.4 (adults 18–49).
  • Episode transcript [2].

Costume Notes[]



Space Invaders


Green Striped




Queen Mary


Green Lantern Jersey


Blue w Gray Dots

The episode opens to Sheldon in his orange Space Invaders shirt. When he goes to talk to Penny, he sports a green on green striped t-shirt. Trying to pass off their lie to Penny, Sheldon is seen in a red and gray fractal pattern shirt. After visiting the ship, he sports an appropriate Queen Mary shirt, presumably fromthe ship's gift shop]. The rest of the episode finds Sheldon in his Green Lantern athletic jersey t-shirt, until the last scene where he sports a blue t-shirt with horizontal stripes of small gray dots










Leonard starts the episode in an unknown tee with a global graphic, possibly related to weather or satellite tracks (hard to tell with his darn jacket on all the time). Then he wears his adrenaline molecule shirt and an olive drab shirt with the radioactive emblem. In the final scene he sports a red shirt with unknown design (due to the jacket, again).



Flash bolt buckle


  • Sheldon poses the following riddle to Leonard: "Assuming all the good Terminators were originally evil Terminators created by Skynet, but then reprogrammed by the future John Connor, why would Skynet, an artificial computer intelligence, bother to create a petite hot 17 year-old killer robot?" He is referring to Cameron from Terminator: The Sarah Connor Chronicles, who is played by Summer Glau. In "The Terminator Decoupling", Summer Glau guest stars as herself.
    • The simple answers to Sheldon's riddle are that Cameron was conceived in line with James Cameron's vision of Terminators being able to blend in with the human race; and that Cameron's own fictional backstory was to replace Allison Young, one of John Connor's most trusted resistance fighters.
  • Despite being described as a mysaphobe, Sheldon takes out the packed chicken he had previously thrown in the garbage can for consumption later, as he doesn't like waste as well. While the chicken was protected in a container inside a bag, the bag and Sheldon's hands were contaminated by the bin, thus compromising the integrity of everything else.
  • Sheldon's focus on Leonard's lying may be very poignant. Cleckley and Hare came up with a checklist of qualities shared by most studied sociopaths. They include: a grandiose sense of self, lack of remorse or shame, shallow emotions, need for stimulation, lack of empathy, poor impulse control, inability to perceive anything wrong with themselves, and the exercise of despotic control. Sounds a lot like=e Sheldon.
  • Raj and Howard only appear in one scene of this episode.
  • After Howard says "So, road trip to Long Beach!", Leonard sits in Sheldon's spot. Sheldon either doesn't notice or care.
  • First episode where Sheldon knocks on a door repeatedly while saying someone's name; however, he knocks four times in this episode as opposed to three.
  • There is "RMS Queen Mary merchandise in Leonard's room after they get back from the "road trip.
  • Sheldon knows some neuroscience, presumably from the Journal of American Neuroscience, which he mentioned earlier this season. Unsurprisingly, this season is two seasons before Amy Farrah Fowler, a neuroscientist is introduced though her degree was based upon Mayim Bialik's own doctorate.
  • The second episode where a character wishes they were more dangerous at an earlier time when bothered by another character. The first was "The Luminous Fish Effect".


Sheldon: I was analyzing our lie, and I believe we're in danger of Penny seeing through the ruse.
Leonard: How?
Sheldon: Simple: If she were to log onto, click on "Upcoming Events", scroll down to "Seminars", download the PDF schedule, and look for the seminar on molecular positronium, well then, bippity-boppity-boo, our pants are metaphorically on fire.

Toby: The Philippines. 1992. The Subic Bay Naval Station. A young boy on the cusp of manhood. His only companions mongrel dogs and malarial mosquitoes. Desperate and alone he reached out to a man who promised to introduce him to a merciful, loving God, but who instead introduced him to a gin pickled tongue shoved down his adolescent throat. What choice did he have but to drink, shoot and snort his pain away?!

Sheldon: Remember how Leonard told you we couldn't come to your performance because we were attending a symposium on molecular positronium?
Penny: ... I remember symposium.
Sheldon: Yes, well, he lied.
Penny: Wait, what?
Sheldon: He lied, and I’m feeling very uncomfortable about it.
Penny: Well imagine how I’m feeling.
Sheldon: Hungry? Tired? I’m sorry this really isn’t my strong suit.

Toby: And that he loved the companionship and the wisdom that his own father failed to provide.
Sheldon: Your parents made the right decision. (walks into his room)
Toby: I cannot work like this!