The Staircase Implementation

​The Staircase Implementation is the 22nd episode of The Big Bang Theory 's third season. It aired on May 17th 2010. This episode reveals why the elevator has always been broken.

Summary
Penny is about to do her nails, when she hears Leonard and Sheldon fighting over the thermostat setting. Leonard comes over to Penny's apartment and asks if he can sleep on her couch. When Penny remarks that Leonard is nuts for living with Sheldon, he tells Penny the story of how he first met him seven years ago. And so begins the flashbacks.

Leonard starts out with explaining how he just started at Caltech and he needed a room for rent. The elevator was still working in the apartment and he sees Sheldon's previous roommate leaving and warning him about Sheldon's idiosyncrasies. He does not heed this warning, thinking the previous roommate was the crazy one. Leonard runs into their transvestite neighbour's apartment by mistake and then meets Sheldon who still looks the same after all these years, in contrast with Leonard, who wears Raj's style of clothing, grows his hair out to the point it is curly and tortoise shell glasses. Sheldon quizzes Leonard about science fiction trivia questions and remarks and allows him to enter after he answers correctly. Sheldon gives a series of interview questions to verify whether or not Leonard is a good and worthy roommate to have and gives him a tour, which involves his future room having "DIE SHELDON DIE" on it, painted on by the previous roommate. At this point, Sheldon's apartment is far more empty, having only two lawn chairs instead of the couch and airchair, although he sits in the lawn chair in the same position of his "spot". After working out seemingly countless pages of the "roommate agreement" Leonard moves in.

Penny cannot understand how Leonard decided to stay with him after all that and has no sympathy for him. Leonard tells her about when Sheldon kicked Joyce Kim, Leonard's girlfriend, out of the apartment. This shocks Penny and asks why he still stayed after that. Leonard tells her it turned out to be a good thing as Kim was a North Korean spy and Leonard had been working on a top-secret rocket fuel for the government: Joyce Kim was trying to seduce Leonard for information, which proved unsuccessful as she then defected back to North Korea. Penny now knows half of the story now: Leonard stayed with Sheldon to protect him from going to prison from what could have happened.

Leonard mentions that the other part has to do with the elevator's destruction and he continues the story. Sheldon comes home from work and he meets Raj and Howard who work at the university too. He finds that Leonard has replaced Sheldon's lawn chairs with the beloved sofa, which Sheldon isn't to happy with initially. Soon, after a lot of switching spots, Sheldon finally claims his "spot" on the couch. After the other guys leave due to Sheldon's antics, they go to Howard's place, where a young masculine voiced Mrs. Wolowitz asks if he has new playmates.

They discover that Howard has a rocket, which only needs fuel to get it going. Leonard tells Penny that he had some rocket fuel in the apartment and they went back to make some. But Sheldon notices he did not do the math correctly, however, and the fuel starts burning. Leonard attempts to take it outside via the elevator. But Sheldon knows how long he has until it explodes, so he pushes Leonard out and sends it down, and soon after the doors close, a loud explosion takes place, explaining why the elevator no longer works. Leonard explains his continued friendship with Sheldon by pointing out that Sheldon saved his life and didn't rat him out to the landlord, the police, or Homeland Security.

While Penny gets a little annoyed at the fact he is the reason that she has to use the stairs everyday, Leonard asks her what she did when she was young seven years ago. While she lies to him, it is revealed to the audience that she was almost a teenage mom, but the pregnancy test shows negative, much to the relief of Penny and her boyfriend.

Leonard goes back to the apartment and apologises for his argument over the thermostat to Sheldon. However, when Leonard turns the T.V. on and it is Babylon 5 that is showing, a whole new fight starts again, with Penny laughing at it as she is packing up her manicure set.

Title reference: After a failed experiment renders the elevator useless, the staircase has to be used (and is therefore often featured as a setting for conversations between various characters). The producers also noted that the apartments do not need the long hallway that apartment floor sets usually have.

Quotes

 * (Penny is about to do her nails)
 * Penny: OK Babydoll Pink, let's see if you can cover up the fact that I got my dad's feet.
 * (Leonard and Sheldon have started fighting which can be heard from Penny's place)
 * Leonard: 2 degrees Sheldon! I just wanna turn up the thermostat by 2 degrees!
 * Sheldon: Let me point out that 2 degrees can be the difference between water and steam!
 * Leonard: Yes, if we lived in a tea kettle!
 * Sheldon: This is the temperature you agreed to in the roommate agreement!
 * Leonard: Aw, screw the roommate agreement!
 * Sheldon: No, you don't screw the roommate agreement, the roommate agreement screws you!
 * Leonard: You know what?! Go to hell and set their thermostat!
 * Sheldon: I don't have to go to hell! At 73 degrees, I'm there already!
 * (Leonard slams their door and knocks on Penny's.)
 * Penny: Who is it?
 * Leonard: Leonard.
 * Penny: Hang on.
 * (She walks on her heels to get to the door so she doesn't ruin her nail job.)
 * Leonard: Can I sleep on your couch tonight?
 * Penny: Uh, well you can try, but the people across the hall are being very noisy.
 * Leonard: You heard that, huh?
 * Penny: Apparently, the one fella tried to adjust the thermostat, then the other fella went bat-crap crazy.
 * Leonard: So you agree, he's nuts!
 * Penny: Well, not as nuts as the guy who chooses to live with him.
 * Leonard: Believe it or not, he was worse when I met him.
 * Penny: (Naively chuckles) Oh, I do not believe that.
 * Leonard: You are so naive. Just like I was seven years ago.
 * (Leonard starts telling the story of how he met Sheldon.)
 * Leonard: "I just started at the university."
 * (It is the year 2003 and we see that when Leonard was younger, he originally had a "classic" Weird Al hairstyle, tortoiseshell glasses and Raj's current attire. He then sees Sheldon's previous roommate leaving the elevator, which was still operational at the time.)
 * Leonard: Hi, excuse me, I'm looking for Sheldon Cooper's apartment?
 * Ex-Roommate: Oh, I bet you're here to check out the room for rent?
 * Leonard: Yeah.
 * Ex-Roommate: Run away dude!
 * Leonard: What?
 * Ex-Roommate: Run fast, run far!
 * (Back in 2010)
 * Leonard: That should have been my first clue.


 * 
 * Leonard: (voiceover) Anyway, I went upstairs and knocked on the door.
 * (2003 Leonard walks over to 4B's apartment and knocks. The door is opened and he is confronted by a large muscular African-American man with breasts and dressed as a woman)
 * Louie/Louise: Yeah?
 * (Long pause, as Leonard is speechless. Louie gives him an impatient look)
 * Leonard: ... Dr. Cooper!?
 * Louie/Louise: Nah, you want the crazy guy across the hall.
 * Leonard: (voiceover) In retrospect, that was clue number 2.


 * 
 * Sheldon: What is the sixth noble gas?
 * Leonard: What?
 * Sheldon: You said you're a scientist. What is the sixth noble gas?
 * Leonard: Uh, radon?
 * Sheldon: Are you asking me or telling me?
 * Leonard: Telling you?
 * (Sheldon gives Leonard an impatiently angry look)
 * Leonard: Telling you.
 * Sheldon: All right. Next question. Kirk or Picard?
 * Leonard: Oh, uh-- Well, that's tricky. Um-- Original Series over Next Generation, but Picard over Kirk.
 * Sheldon: Correct. You've passed the first barrier to roommatehood. You may enter.


 * 
 * (Leonard is about to sit in a lawn chair)
 * Sheldon: No, that's where I sit!
 * Leonard: What's the difference?
 * Sheldon: This seat is ideally located, both in relation to the heat source in the winter and a cross breeze in the summer. It also faces the television at a direct angle, allowing me to immerse myself in entertainment or gameplay, without being subjected to conversation. As a result, I've placed it in a state of eternal dibs.


 * 
 * (Sheldon is busy getting Leonard to sign the roommate agreement)
 * Sheldon: Roommates agree that Friday nights shall be reserved for watching Joss Whedon's brilliant new series, "Firefly".
 * Leonard: Does that really need to be in the agreement?
 * Sheldon: Well we might as well settle it now, it's gonna be on for years.


 * 
 * Sheldon: Mmm, I assure you, you'll be sorry you wasted your money on an iPod, when Microsoft comes out with theirs.
 * Raj: OK, do you have an opinion about everything?
 * Sheldon: Yes.
 * Howard: You just assume you're always right?
 * Sheldon: It's not an assumption.


 * 
 * Leonard: Oh, it's time for Babylon 5.
 * Sheldon: But we don't watch Babylon 5 in this apartment.
 * Leonard: Why not?
 * Sheldon: Because no one likes Babylon 5.
 * Leonard: Well, I like it.
 * Raj: Me too.
 * Howard: So do I.
 * Leonard: There you go, 3 against 1.
 * Sheldon: They don't get a vote. It's 1 against 1 and according to the roommate agreement, all ties will be settled by me.
 * Leonard: But I said no to that.
 * Sheldon: And I said yes. And I settle all ties.


 * 
 * (In 2003: Leonard, Raj and Howard are at Howard's place after leaving Sheldon. Howard's mother, who had an even younger, louder and very masculine voice at the time, is yelling at Howard.)
 * Mrs. Wolowitz (shouting from another room): HOWARD, ARE YOU HAVING A PLAYDATE?!
 * Howard: (also shouting back): I DON'T HAVE PLAYDATES, I HAVE COLLEAGUES!
 * Mrs. Wolowitz: DO THEIR PARENTS KNOW THEY'RE HERE?!
 * Howard: NO, BUT IF YOU KEEP SCREAMING, MAYBE THEY'LL HEAR YOU!
 * Leonard: Is that your dad?
 * Howard: If she grows anymore hair on her face, yes.


 * Mrs. Wolowitz: HOWARD, WHAT HAPPENED TO THE OREOS I LEFT ON THE COUNTER?!
 * Howard: I HAVEN'T SEEN YOUR OREOS! (Doesn't notice that Raj is eating them) JUST TAKE YOUR BATH WITHOUT THEM!


 * 
 * (Leonard has just told Penny that Howard had a model rocket and only needed some of the fuel that Leonard was making for the government to get it going)
 * Penny: So why was it his lucky day?
 * Leonard: Well it turns out I had a little rocket fuel in the apartment.
 * Penny: What were you doing with rocket fuel in your apartment?
 * Leonard: Well, Joyce Kim was kind of curious about what I did for a living, and I was gonna, kinda...show it to her. It's not important, the point is the guys and I went back to the apartment.
 * Penny: OK, but are we ever going to get to the elevator?
 * Leonard: Yeah, were really close, we're at the apartment....
 * (In 2003: Leonard is incorrectly mixing rocket fuel for Howard's model rocket.)
 * Leonard: The trick is to mix it in a Tovex in order to create a combustible gel that will generate over 8000 kilonewtons of thrust.
 * (Howard and Raj excitedly chuckle)
 * Raj: Coooool!
 * Sheldon: Won't work.
 * Leonard: Excuse me, but I've been working on this a long time. Trust me, it will work.
 * Sheldon: You don't see your mistake, do you?
 * Leonard: There's no mistake.
 * Sheldon: This is for a full scale rocket, not a model.
 * Leonard: Well I've adjusted the formula.
 * Sheldon: Not correctly.
 * Leonard: OK, I've had it with you! You might be an expert on theoretical physics, and science-fiction programs, and where to sit on a freaking couch! But this is "applied" physics, and when it comes to applied physics.... (rocket fuel starts sizzling) ..... Ahh, uh-oh.
 * Howard: What's happening?
 * Leonard: A bad thing, a veerry bad thing. Get the door! Get the door! Get the door! Get the door! Get the door!
 * (Sheldon turns their apartment's flag upside down, while the other 3 go out into the hallway where Leonard waits for the elevator.)
 * Howard: You're waiting for the elevator?!
 * Leonard: Oh, right!
 * (Leonard starts to go down the stairs, when the elevator arrives.)
 * Raj: Wait, it's here!
 * Leonard: Ahhhhhhh! (Goes back up and into elevator. As the door closes, Sheldon barges past Raj at an unusually quick pace, pushes the elevator doors back open and takes the rocket fuel out of his hands.)
 * Sheldon: Give me that! (Pushes Leonard out, presses the down button and exits the elevator. The doors close)
 * Leonard: What did you do that for?! I had plenty of time-!
 * (There is a sudden, very loud explosion in the elevator, destroying it. All of them, except Sheldon are in shock and horror.)
 * Sheldon: You're welcome. (Sheldon goes back inside, with Leonard still dazed.)
 * (In 2010)
 * Leonard: Not only did Sheldon save my life, he didn't rat me out to the landlord. Or the police, or Homeland Security.
 * Penny: OK, so basically, you're the reason I have to walk up and down 3 flights of stairs everyday?
 * Leonard: So, I did something stupid, I'm sure you did stupid things when you were younger; what were you doing 7 years ago?
 * Penny: Excuse me, I was in high school, studying, keeping my nose clean, doing volunteer work for the community...
 * (In 2003, a teenage Penny back in Nebraska with a boyfriend, is doing a pregnancy test.)
 * Penny: Not pregnant. Yes! (High-fives boyfriend.) Ha ha!

Trivia

 * In this episode, the hitherto unseen characters of Joyce Kim, a North Korean spy who dated Leonard, and the pairs' original neighbour, Louie/Louise, the "two hundred pound transvestite with a skin condition" are seen.
 * Sheldon's lawn chair faced the television at a direct angle, thus discouraging conversation. But as explained in the Pilot and The Gorilla Experiment, his spot faces the television at an indirect angle, thus encouraging conversation. (Apparently over the years he learned to tolerate company.)
 * During the second of three sets of questions, Sheldon asks if Leonard has a vehicle. Leonard has a car, but asks, "Can't you drive?" And Sheldon confesses that "I can. I choose not to."
 * Sheldon makes two blatantly wrong predictions in flashbacks: Firefly would run "for years" and told Raj that he would be sorry he wasted his money on an Apple iPod when Microsoft "comes out with theirs" (implying the the Microsoft Zune would be more popular than the iPod series). In reality, Firefly only lasted for one season, and the Microsoft Zune dwindled in sales from the moment it was released, while the iPod became a Global Icon when it comes to music players.
 * In Howard's room of 2003 they showed a Roboraptor and a slimline PS2, neither of which was available then (he most likely got elected for testing them since he has a master's degree in engineering).
 * While forming the room mate agreement Sheldon finishes the section for television & movies and moves onto section 9: miscellany, making television and movies section 8. However, in the flashback with Joyce Kim in Leonard's bedroom, Sheldon states that section 8 is visitors (most likely, section 8 was for both).
 * When Leonard, Howard, and Raj are playing on Sheldon's Nintendo Gamecube, you can closely hear the Waluigi Stadium music from Mario Kart: Double Dash.
 * The present Leonard in 2010 refers to events seven years ago (2003) and states, "I’d just started at the university." The past Leonard introduces Howard and Raj to Sheldon with, "They work at the university, too." These allusions to such an early point in time at the university, perhaps unintentionally, imply some of the main characters are not faculty members in the flashback. Since Leonard was born in 1980 (The Alien Parasite Hypothesis), and got his doctorate at twenty-four (The Cooper-Hofstadter Polarization), he was not finished with graduate school when he started at Caltech. Similarly, Rajesh was born in 1981 (The Grasshopper Experiment), which means at twenty-one or twenty-two years old, he probably wasn't finished with graduate school either. Howard, also born in 1981 (The Bad Fish Paradigm), only has a master's degree, thus, the chronological events presented may not be a continuity concern regarding his character. Note this possible mistake has no bearing on child prodigy Sheldon, though. Further, Leonard must have completed his doctoral studies at Caltech, working as a graduate research assistant, and the same can likely be said of Raj.
 * Although the episode The Nerdvana Annihilation, Season 1, in 2008, Leonard claims that the elevator has been broken for two years (2006). This episode reveals that the elevator has been broken since 2003.
 * Given the year of 2003, the episodes of Firefly that Sheldon is referring to places the episode's date(s) in 2003 between June 28 and December 13.
 * The Jerusalem Duality: Penny: "I don’t understand, exactly how did he get any friends in the first place?" Howard: "We liked Leonard." The episode of this article clearly establishes that.
 * Sheldon gets upset when someone phrases a response with an air of uncertainty, as when he asks Leonard about the sixth noble gas. This is also evident in The Dead Hooker Juxtaposition, when Alicia pondered "freakishly feline."
 * Sheldon says to Leonard, as he introduces his room, "Huzzah!" He previously said this while discussing fifteenth century historical inaccuracies at the Renaissance Fair in The Codpiece Topology.
 * Sheldon put Leonard in his spam folder after he forwarded him a picture of a cat playing the piano, entitled "This is Funny." In The Panty Piñata Polarization, Sheldon told Penny she violated his rule about forwarding email humor, the photo of the cat who wants to “has cheezburger," and gave her a "strike." Sheldon considers LOLcats Internet banality.
 * One of Leonard's whiteboards contains an analysis of hydrazine propulsion systems, specifically, the chemical equation for the spontaneous exothermic decomposition of hydrazine, followed by an equation for the endothermic dissociation of ammonia into hydrogen and nitrogen. Referenced thrust values, including those for the Space Shuttle Main Engine (SSME) and Saturn-V, are also provided. Sheldon's work on his whiteboards are on Ginzburg-Landau Theory.
 * It is revealed that Sheldon owned a Palm Treo.