The Big Bang Theory

The Clean Room Infiltration

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"The Clean Room Infiltration" is the eleventh episode of the eighth season of the American sitcom The Big Bang Theory. The episode aired on Thursday, December 11, 2014.


Amy hosts a traditional English Victorian Christmas Eve dinner for the gang while the guys are conducting an experiment in the university clean room and accidentally let a bird in. Raj's father comes for a visit. To prove a point to Amy, a Scrooge-like Sheldon buys her the perfect gift to ruin her Christmas.

Extended Plot

At dinner in Apartment 4A, Raj tells everyone that his parents are divorcing and getting themselves lawyers. Sheldon would not hire the She-Hulk as a lawyer, if he ever needed one. Penny compliments him for almost staying on topic for once. Sheldon adds that since she is the only monster at her law firm, she must be an affirmative-action hire. Since Raj's father is visiting, he can't host Christmas eve dinner so Amy volunteers since she always wanted to host a traditional English Victorian Christmas for gang including parlor games, goose, figgy pudding. Sheldon doesn't like figgy pudding because of all of the raisins and won't come. Amy replies that he is coming. Sheldon claims that she hates him; however, Amy corrects him that she loves him, Sheldon adds that there are still a lot of raisins in it. Raj is a little miffed about themed-holidays since they didn't like his "Tom Hanks"-giving, and is peeved when everyone takes an interest in Amy's Victorian theme. 


Sheldon trying to hurt Amy by giving her a gift.

On Christmas Eve, Leonard and Howard are in contamination garments in the university cleanroom constructing an experiment to detect cosmic particles. Leonard likes the fact that he has no allergy problems due to the sterile room. A pigeon flies in the room because Howard left the loading dock door open. Now they have to get rid of it before the bird soils the dust-free room. Howard doesn't want to call facilities and get blamed. First he suggests they turn off all the lights except for one, but that is to attract moths. At Amy's apartment, Amy and Penny are visiting with Raj and his father who has nothing good to say about his wife. On his twenty hour airplane flight without his wife, he didn't pray for the plane to crash. The guys call Raj to help them deal with the pigeon. Dr. Koothrappali stays with the girls since he just had a long flight which doesn't make Penny happy.


Dr. K won the yarn game.

Bernadette has picked up Sheldon and is singing Christmas carols about Santa Claus in her car with too much Christmas joy until Sheldon turns off the music. Sheldon's uncle did many of the things that Santa is known for and got arrested.  He and Amy decided not to get each other something for Christmas since Sheldon doesn't enjoy it. While they were Christmas tree  shopping, Amy kissed him under the mistletoe in public making Sheldon very unhappy. He felt he was part of a Tijuana sex show. Sheldon has decided to punish her to make her feel as miserable as he does so he is going to buy her a Christmas present. Since she has not gotten him one, that would ruin her Christmas and make her guilty and sad according to Sheldon's logic. She should be so unhappy that she won't make him celebrate the holidays ever again.

Howard is trying to catch the pigeon in a garbage bag with a Slim Jim which, Leonard thinks is stupid. He just wants to call building services. Howard doesn't want to get the blame even though he always tries to hide his culpability. Raj arrives and wants to know the situation. Leonard explains that Howard wants to catch the bird in a garbage bag with a Slim Jim, which he holds up and the pigeon snatches and flies off.

Back at Amy's place, Dr. Koothrappali thinks that it is too soon to think about dating again. Penny volunteers if she were free and he didn't talk about Star Trek all the time. Amy brings out her first parlor game that involves blowing a ball of wool across a table. Penny also tells Raj's father that Amy is also taken.

While trying to catch the pigeon, Howard tells Leonard that he is jealous because they used to be best friends till Raj came along. Leonard thinks that happened because Howard can push Raj around. Then they start arguing who is smarter and conclude that both Raj and Leonard are smarter than Howard though since it's Christmas, they decide that Howard is smarter one. Howard decides to make Raj get the bird out, but Raj is sure that it was Howard that let the pigeon in, scoffing at the idea that Leonard would do something like that.

Bernadette and Sheldon are shopping for the perfect gift to ruin Amy's Christmas. Bernadette's favorite gifts from Howard were based upon what Howard knew about her. Amy likes Chaucer, medieval literature and old French movies which make her eyes light up according to Sheldon. He also like the way her fingers dance around whenever she hears harp music. He does admit that he really loves Amy and wants to find a gift to make her feel small and worthless.

Amy and Raj's father are now blowing the ball of wool back and forth across the table with increasing boredom. Dr. Koothrappali wins though Penny quips that it probably doesn't feel that way. He remembers the theme parties that his wife used to throw. She and Raj spent a lot of time together since he worked a lot. Penny brings up Raj's girlfriend Emily, who also works a lot. She thinks that that is funny, but Dr. Koothrappali is not amused.

Sheldon is now sitting on Santa's lap telling him that he wants their picture together to punish his girlfriend for making him celebrate Christmas. Santa thinks that dating Sheldon is punishment enough, to which Sheldon states "There's an argument for that, but I want to make sure". They smile for the camera.

Sheldon in the Christmas spirit?

Back in the clean room, they are trying to catch the bird with a blanket and a fire extinguisher to get him out the door. Leonard has the fire extinguisher, Raj is standing by the door to open it, and Howard has the blanket and then complains that they don't think he is smart enough to use the fire extinguisher. They trade tools and Howard attacks the pigeon with the fire extinguisher which causes the bird to fall dead onto the floor. Howard is upset because that something similar happened when he was a child, (he had sat on a blue jay) and then he tried to revive the bird with electricity, setting the poor thing's corpse on fire. The bird is not breathing so Howard gives it CPR thus reviving the bird. As they carry the bird toward the door to let him out, a crow flies into the room because no one has yet closed the door. As the crow looks down at the guys, they debate calling building services on Christmas Eve. Penny calls Leonard and just tells them to leave as it's Christmas Eve and nobody would know they were in there to begin with. Even though they signed into the clean room, she tells them to erase their names off the list and get out of there. The next scene implies that they did just that, as it shows them in the car singing "Jingle Bells" heading toward the party.

After finishing the figgy pudding, Sheldon first complains about the raisins. Amy tells him that they were figs, so Sheldon is fine with that. Dr. Koothrappali offers to help; however, since he Heimliched a ball of wool out of her, he didn't have to. Sheldon gives Amy his gift of his picture with Santa in a frame that plays a personal Christmas greeting to her from him and she loves it. Sheldon tells her that she got him nothing expecting her to be sad. He is happy because they will never do it again. Despite what she said, she made Sheldon a gift, his favorite cookies from his Meemaw's recipe. Amy talked to her to get the recipe. Sheldon tries one and calls them perfect because they taste like her hug. Amy wishes Sheldon Merry Christmas. Everyone is happy and Sheldon wonders if giving is what Christmas is all about in a softer gentler tone. Raj ends Sheldon's festive mood when he reaches for one of his cookies and Sheldon slaps his hand, telling him to take his hands off them.

Finally, with the party still occurring, Amy wants them all to sit down and play "Hot Boiled Beans." Amy explains that one person leaves the room while the rest hide a small item in the room. The first person is invited back in by saying, "Hot boiled beans and bacon for supper, hurry up before it gets cold!" Raj shakes his head and claims that if they think this holiday theme is better than his idea for a "Tom Hanks"-giving, then they are all crazy.

The gang having Christmas dinner together.


Raj's father visits.



  • Title Reference: The refers to the pigeon that Howard let into the clean room they were working in.
  • Taping date: November 18, 2014
  • Chuck Lorre Vanity Card
  • This episode was watched by 15.49 million people with a rating of 3.9 (adults 18-49).
  • Total viewers including DVR users 20.98 million.
  • The Big Bang Theory was ranked #x for the week ending xx December 2014.
  • This episode aired in Canada on December 11, 2014 with 4,297 million viewers with a weekly ranking of #1.
  • In Australia, it aired on March 3, 2015 with 0.87 million viewers.
  • Episode transcript [1]
  • Chuck Lorre's vanity card


  • Jesse Schedeen at IGN - The Big Bang Theory had hit a nice little groove lately, but some of the momentum was lost in this holiday episode. The scenes involving Leonard, Howard, and Raj testing their mettle against a pesky pigeon were very entertaining. Unfortunately, most of the actual holiday material was pretty bland, and only the emotionally upbeat finale really salvaged it. There's no reason things can't pick up when the show returns in January, though. [2]
  • Dhruv Rao of The DR Club (B-): "The lackluster main plot this week couldn't be saved by the well-executed subplots. The combination of the three plots was definitely not a good holiday gift for the viewers: it was as though the audience was eating a meal in which the appetizers and the dessert rocked, but the main course bombed. No one would be satisfied by the end result of that, as the audience would still be hungry for a proper "meal"."
  • IMDb user reviews [3]


  • First visit of Raj's father to Pasadena. This episode is his first appearance since "The Transporter Malfunction" (S5E20).
  • Howard seemingly contradicts the original history where Leonard met Howard and Raj together at Caltech and not Howard first as depicted in "The Staircase Implementation" (S3E22).
  • First time all the gang have been together in Amy's apartment.
  • Sheldon went Christmas gift shopping for Penny in "The Bath Item Gift Hypothesis".
  • Fifth Christmas themed TBBT episode.
  • The first time Penny and Raj's father have seen each other since "The Griffin Equivalency" (S2E4).
  • Although both are recurring characters, this episode marks the first time either of Raj's parents appear on the show in person in Pasadena. As a result Amy is the only main character who does not have a parent who has been in Pasadena.
  • This is the second episode where Leonard, Raj, and Howard are seen wearing white hazard suits. The first being "The Engagement Reaction" (S04E23).
  • Sheldon tries to be an Ebeneezer Scrooge, but his plan backfires with Amy loving his present and her returning the gesture.
  • Amy has contacted Sheldon's Meemaw.
  • Dakin Matthews again plays Santa as he did in Sheldon's dream in "The Santa Simulation".
  • This episode marks the first scientific collaboration between Leonard and Howard at Caltech, showcasing the former's expertise in astroparticle physics and the latter's expertise in astronomical instrumentation. Together, they built a multiwire proportional counter for detecting cosmic particles. Leonard marvels at how their multiwire-type detector can replace an entire array of giant Cherenkov telescopes.
  • Second episode where a bird trespasses into a building. First was "The Ornithophobia Diffusion".
  • First episode with a plot with most scenes where Sheldon and Bernadette are the only main characters that appear.
  • This episode marks the 100th appearance/episode of Bernadette.
  • Penny asks Dr. Koothrappali how much he talks about Star Trek. The actor who plays him (Brian George) actually was on Star Trek; he played Dr. Bashir's father on Star Trek: Deep Space Nine.
  • Dr. Koothrappali's animosity towards Leonard seems to have mellowed significantly since his last contact with him, back when he was dating Priya; however, he tries to tell Penny stories of his own bad marriage, trying to urge her not to follow his own example.
  • When taunting Amy about having no Christmas gift to offer, Sheldon asks if she wishes she were Jewish, prompting Bernadette glance inquiringly at Howard. The actors playing Bernadette and Amy (Melissa Rauch and Mayim Bialik) are both Jewish playing Christian characters.
  • In this episode, Amy throws a Christmas party with a Victorian theme. Coincidentally, Amy's actress, Mayim Bialik, also had a wedding ceremony with a Victorian theme.


(The opening apartment scene with the gang having dinner)
Penny: Hey, how are things going with your parents?
Raj: Not great. They hired divorce attorneys.
Sheldon: You know, speaking of attorneys, if I ever needed a lawyer, I would not hire She-Hulk.
Penny: (happy but mad) You know what? That was almost on topic. I’m gonna say good job, Sheldon.
Amy: Wait, She-Hulk’s a lawyer?
Howard: Yeah, she works at a law firm in New York.
Sheldon: Yes, but she’s the only monster at the firm. Between you, me and the wall, I think she’s an affirmative action hire.
Raj: Anyway, Dad’s gonna be here in town, so I won’t be able to do Christmas dinner this year.
Amy: If you’re not up to hosting Christmas dinner, I’m happy to do it. You can even bring your father.
Raj: (proud) That would be nice.
Amy: I’ve always wanted to do a traditional Victorian Christmas. Parlour games, goose and figgy pudding.
Sheldon: (disgusted by this) Ugh. English pudding. You get yourself all excited for pudding, and here comes a cake with raisins in it. I’m not going.
Amy: You’re going.
Sheldon: Why do you hate me?
Amy: I don’t hate you. I love you.
Sheldon: (lovingly) Well, you call it love, but it has a lot of raisins in it.
Raj: Amy, good luck getting these guys excited about a dinner with a theme. I gave up when no one cared about my Tom Hanks-giving.
Bernadette: (excited) I think a Victorian Christmas sounds nice.
Howard: I agree.
Leonard: Why not?
Penny: Me, too.
Raj: (shocked) You guys suck.
(The 'Howardette' couple, Leonard and the 'Shamy' duo ignore Raj's comment. Opening theme begins).

Leonard: Can you believe there was a time when we would have needed an array of the giant Cherenkov telescopes to detect cosmic particles? And here we are building are own multi-wire detector like a couple of bad asses.
Howard: Yeah. If we were still single, we'd be trippin' over that booty.

Penny: So, Dr. Koothrappali. Long flight?
Dr. Koothrappali: 20 hours.
Penny: Oh, that's rough.
Dr. Koothrappali: Not at all. Did you know when you fly transcontinental without your wife, you don’t pray for the plane to crash?

(The scene of Bernadette's car)
Bernadette: (singing) Here comes Santa Claus, here comes Santa Claus, right down Santa Claus Lane. (pan to a grumpy Sheldon sitting next to her) Vixen and Blitzen and all his reindeer pulling on the reins.
Sheldon: Yeah, I appreciate the ride.
Bernadette: (singing): Bells are ringing, children singing, all is merry and bright. (close-up of Sheldon's 'I'm turning it off' expression) So hang your stockings and (back to Bernadette singing for the final time) say your prayers ’cause Santa Claus (The music is now turned off) is coming tonight. (she now asks Sheldon crossly) Why’d you turn it off?
Sheldon: Because in the last ten minutes, Santa came to town, kissed Mommy and ran Grandma over with a reindeer.
(Bernadette suddenly reacts crossly at Sheldon's remark)
Sheldon: I had a drunk uncle who did all those things. Nobody sings songs about him.
Bernadette: (smiling crossly at this) Maybe you’d like it more if you thought of Santa as a superhero and his power is bringing joy to children.
Sheldon: My uncle was accused of that, too.
(Bernadette frowns for a bit)
Sheldon: It turned out to be legal in Oklahoma.
Bernadette: Okay, new subject. Let’s talk about presents. What did you get Amy?
Sheldon: Oh, we’re not exchanging gifts.
Bernadette: (crossly) Come on Sheldon, you have to get her something.
Sheldon: Why should I? She knows I don’t like Christmas and yet every year see forces me to celebrate it. Not am I going to this foolish dinner against my will. At the Christmas tree lot, there was mistletoe and she kissed me under it in public. Like we were the stars of a Tijuana sex show.
Bernadette: (through her mad smile) She’s just excited about the holidays.
Sheldon: Yes and she’s not taking my feelings into account at all. Maybe it’s time I teach her a lesson.
Bernadette: (puzzled) How?
Sheldon: Hmm. (thinks) I’d have to do something heinous; something that makes her as miserable as she is making me. Oh, I've got it. This is good.
Bernadette: (with a shifty smile) What?
Sheldon: I’m going to buy her a present.
Bernadette: (happy and cross) Yeah, you’re gonna have to walk me through that.
Sheldon: With gift giving, there’s an implied social contract. If I show up tonight with a present and she doesn't have one for me she’ll feel terrible.
Bernadette: (now slightly too cross) Then you’re both sad?
Sheldon: Yes. Maybe she’ll feel so guilty she’ll never make me celebrate the holidays again.
Bernadette: (asks Sheldon crossly for the last time) So your evil plot is to buy your girlfriend a present?
Sheldon: That’s right. So stay on my good side or I’ll get you a little something too.
(Bernadette continues to drive and smile crossly while she is ignoring Sheldon)

Howard: Why do you keep assuming it was me?
Leonard: Because you do this kind of thing all the time and then you try to cover it up.
Howard: Like when?
Leonard: Ack! What about when you flipped the Mars Rover, or lost Koothrappali’s dog, or almost drove off with that baby?
Howard: (annoyed) Again, it looked like my car, and the baby didn't even cry until his mother punched me with her keys!

Santa: All right, let me see if I got this straight. A picture of you on my lap is a way to punish your girlfriend for making you celebrate Christmas?
Sheldon: Correct.
Santa: Santa thinks dating you is punishment enough.
Sheldon: There's an argument for that, but I want to make sure.

(The scene of Bernadette and Sheldon at the shopping mall)
Bernadette: What about that sweater?
Sheldon: No, it’s not good enough. It has to be perfect.
Bernadette: (informs him crossly) I think the nicest gifts I’ve got from Howie show how well he knows me.
Sheldon: Hmm. Let’s see, what do I know about Amy? She loves medieval literature, Chaucer’s her favourite. And her eyes sparkle when she watches old French movies. I enjoy how harp music causes her fingers to dance as if she’s playing along.
Bernadette: (with a low smile) Wow, you really do love her.
Sheldon: I do. Now, let’s find the kind of gift that makes her feel small and worthless.
(Sheldon now walks out of view)

[The dinner scene at Amy's apartment]
Raj: Hmm, Amy, that pudding was delicious.
Sheldon: If you liked raisins
Amy: Thank-you and it’s figs.
Sheldon: Oh, well in that case it was pretty good.
Bernadette: [very worried with Howard] You feeling okay? You hardly touched your goose.
Howard: It smelled too much like blue jay.
Dr. Koothrappali: Can I help you clean up?
Amy: Oh, you Heimliched a ball of wool out of me; you’re good.
Sheldon: Um, what do you say we exchange gifts?
Penny: Oh, Sheldon we didn't bring any.
Leonard: I thought you hate giving gifts.
Sheldon: Yeah, I do. Which is why I got Amy this.
Amy: You got me something?
Sheldon: Oh, not just something, no. It’s from the heart, it’s holiday themed and I swallowed the gift receipt so you cannot return it.
Amy: Look at you in Santa’s lap. That’s so sweet.
Sheldon: Of course it is. It’s the perfect gift. How are you feeling right now? Guilty? Sad? Wishing you were Jewish?
Amy: No. I love it.
Sheldon: Oh, really? Well, how about now?
Sheldon’s recording coming from the frame: Happy holidays to my dear Amy. I hope you treasure this as much as I treasure you.
Sheldon: And you got me nothing. Christmas is ruined. Let’s never speak of it again. Well, this was fun.
Amy: Actually, I did get you something.
Sheldon: But what about our agreement?
Amy: Well you got me something. Here.
Sheldon: Cookies?
Amy: They're your Meemaw’s Christmas cookies. I called and got the recipe.
Sheldon: [Takes a bite] They’re perfect. It tastes like her hugs.
Amy: Merry Christmas, Sheldon.
Sheldon: I can’t believe this. You’re happy. I’m happy. Well, maybe a holiday that’s all about giving isn't so… [Raj reaches for a cookie] Get your hand out of that box.

Amy: Okay. The next game is called: Hot Boiled Beans.
Penny: (crossly) Of course, it is. (sips some wine)
Amy: One person is sent out of the room while the others hide a small item. Then they invite the first person back by saying (in Cockney accent) "Hot boiled beans and bacon for supper, hurry up before it gets cold".
Raj: If you people think this is better than Tom Hanks-giving, you're all crazy.



  • [4] Taping Report by MichyGeary

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