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"The Imitation Perturbation"[1] is the sixth episode of the twelfth season of the American sitcom The Big Bang Theory. The episode aired Thursday, October 25, 2018.


When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween party. Leonard is shocked that Penny doesn't remember their first kiss.[2]

Extended Plot[]

During take out dinner in the Hofstadter's apartment, the subject of the fortieth anniversary of the movie “Halloween” comes up. Missing the point, Sheldon describes the origins of the holiday while Amy wonders if everyone was going to dress up at work. At Bernadette's work, someone once dressed up as a zombie triggering a company quarantine which alerted the CDC. Leonard suggests that they throw a Halloween party. Penny used to throw them at the time though Leonard only remembers being invited to one of them. Howard warns them that his costume is going to be very scary.


Leonard as Inspector Gadget

At Caltech as Sheldon walks down the corridor dressed as Doc Brown from the "Back to the Future" movies, Howard joins him dressed up as Sheldon complete with Flash shirt. Sheldon stares at him and then asks Howard if he did something to his hair. “Yes,” Howard replies as Sheldon walks off and Howard looks astonished at Sheldon's stupidity and obliviousness in recognizing his costume.

In the Caltech cafeteria, Leonard is Inspector Gadget complete with helicopter hat and Raj is Supreme Court Justice Ruth Bader Ginsberg or “Kooth Bader Ginsberg” as Raj wants to be called. Howard joins them dressed as Sheldon as Raj and Leonard laugh at him. “Hello,” exclaimed Howard and the clueless Sheldon in unison which made it all the more funny. After Raj finds Howard guilty of “Killing it” with his costume, Howard then gives them interesting facts about the Supreme Court, the word irritable and the word etymology. Both Raj and Leonard burst out laughing uncontrollably which confuses Sheldon. The guys kid him about his spot and his bathroom schedule. Sheldon is still clueless until Leonard explains Howard's costume. Sheldon then realizes that the duo were laughing at him and not at Howard.

Without costume, Sheldon sulks at his desk while his wife Amy enters in the purple Clara Clayton dress from the third BTTF movie. Sheldon is no longer interested in costumes while Amy reminds him that she put on a corset for him though she prefers to breathe. Sheldon wonders if he tries to correct everyone and complains about everyone laughing at Howard as Sheldon. Sheldon feels that they laugh in a derisive way. Not in an instructive way like he does when they are stupid.

Penny comes home to her apartment decorated and exclaims, "Treat or Treat.” Leonard won't give her any candy until she is in costume. Penny claims to be dressed as a pharmaceutical rep who is also a failed actress who traded constant rejection for a Christmas bonus and dental plan. Then she wonders why women's costumes are always sexy this and sexy that. Leonard then brings up the party that she invited him to and asks what was memorable about it. Penny only remembers throwing up in a pumpkin. Leonard brings up their first kiss together. Penny remembers their first kiss later at his first birthday party when she felt sorry for him. They just remember different things. Leonard remembers falling in love and Penny remembers throwing up in a pumpkin.


“Where were we?”

Amy goes to the Wolowitzes and tries to get Bernadette to have Howard apologize. Bernie thought it was all in good fun. She reminds Amy that Sheldon called Halley “Winston Churchill” and always makes fun of Howard's magic, job and his alma mater. She adds that Sheldon is the problem and that he should take it up with Howard.

At the party, Raj shows up as the Supreme Court Justice Ginsberg and Anu is dressed as the U.S. Constitution. Anu quips that Raj is going to interpret her. Stuart is dressed up as a butterfly using one of Halley's costumes and Bert is dressed up as geologist “Doc” Ewing who won the 1960 Vetlesen prize. Bernadette is Mary Poppins and Howard is Bert the chimney sweep. When he gets home is going to clean out Mary Poppins “chimney”. Penny is a German barmaid. While sitting on the couch, Leonard again reminds his of their first Halloween kiss. Speaking with Raj and Anu, he thinks that an arranged marriage is awesome until he realizes that the woman still gets a choice in the arrangement. Sheldon and Amy show up dressed up as Howard and Bernadette. The Wolowitzes are gobsmacked. Bernadette demands to know what they are doing. Amy says that she is being unnecessarily hurtful in a very sweet voice. Sheldon claims not to understand because he went to MIT. Howard congratulates them and then asks them to go change. Amy says she can't because she has such teeny tiny legs. Sheldon then pulls a quarter out of her nose. Penny and Leonard try to stop the chaos but Raj and Anu let it go on. Watching the chaos, Bert ask Stuart Stuart if this is a good party, to which he confirms in an amused tone.


Sheldon as Howard and Amy as Bernadette

Howard and Bernadette are not speaking on the drive home. Bernadette was hurt and then asks Howard if her voice is that high pitched and annoying. Howard claims that her voice is melodious. Then she wants to know if she is unnecessarily hurtful, but Howard didn't hear that from her melodious voice.

While cleaning up, Penny does admit that she remembers their first Halloween kiss; however, she hated that that was their first since she was drunk and mad at Kurt. She wanted their first to mean something, so that is why she wants the birthday kiss to be their first. Leonard can live with that as their official first kiss. They start to make out until Stuart shows up. Penny sends him out with the trash and then locks the door. “Where were we?”

Sheldon and Amy are having lunch while discussing how hurt Howard's feelings had made Sheldon a better person. Howard comes over and asks them to apologize since Bernadette is very upset about their costumes. Amy would be glad to as soon as Bernadette apologizes for not getting Howard to apologize to Sheldon. Howard then cited Star Wars in the holo-chess scene where R2D2 is told to let the Wookie win.

Bernadette is working in the kitchen while Sheldon enters. Howard let him in and then drove off. Sheldon tells her that he learned that her feelings are hurt. Amy is not the first person to kid her about her squeaky voice. She found it hard to be taken seriously when she was the smallest person in the room. Sheldon felt the same way in high school since he was small and only nine years old. In high school, Bernadette tell him she was “Bernadette the marionette”. The other kids called him egghead. Bernie was made to breath helium and her voice was so high no one except the dog could hear her. They end up agreeing that they are more alike than they thought since they both took a lot of crap from people growing up.


Supreme Court Justice and the US Constitution.

Finally, the guys are sitting down to watch “Halloween” together which Sheldon is finally ready to do. The lights go up and then Amy comes in and asks what the guys think that they are doing. They mention the “Halloween” movie and Amy demands that Sheldon come home because she was forbidding him to watch it. He leaves and then at their door he tells Amy that she took long enough. Amy screams at him that she had just gotten his text.



  • Title Reference: The title refers the gang dressing up as each other for Halloween.
  • Taping date: October 9, 2018
  • This episode was watched by 12.99 million people with a rating of 2.3 (adults 18–49).
  • Total viewers including DVR users 17.56 million.
  • This episode aired in Canada on October 25, 2018.
  • Chuck Lorre's vanity card. [1]


  • Caroline Preece at Den of Geek! - The episode's big argument begins when Howard, perhaps sensing his chance to get one last dig in before the end, dresses up as Sheldon for Halloween. Everyone gets a kick out of it except the joke's subject, who has to have it explained to him before he even realizes he's the object of ridicule. The joke is funny for the audience precisely because it's used sparingly, with Howard quickly changing into a different costume for Leonard and Penny's impromptu party later that evening...Cue Sheldon and Amy returning the favor and turning up to the party dressed as Howard and Bernadette, with the prize going to Amy for her spot-on impression of Bernadette's (notably put on by the actress) high-pitched voice and mannerisms. It's a cutting observation of how Bernadette constantly uses her femininity to get away with being cruel and abrasive, and her rebuttal that she's had to be that way in order for people to take her seriously feels equally true. [2]
  • IMDb user reviews [3]


  • This episode is the last Halloween-themed episode.
  • Penny may not remember her first Halloween kiss with Leonard, but she had been drinking "a lot".
    • She did admit to Leonard after the party that she DOES remember that kiss. Though she did not want to accept it as their first official kiss because she was drunk then and was still with her ex-boyfriend, Kurt.
  • Leonard is dressed up as Inspector Gadget from the 1983 TV series of the same name.
  • Howard is dressed up like Sheldon Cooper for Halloween and Sheldon is dressed up as Dr. Emmett L Brown from "Back to the Future". Sheldon and Amy were dressing like Dr. Emmett L. Brown and Clara Clayton, but they changed costumes in the party dressed like Howard and Bernadette so Sheldon can get revenge on Howard.
  • Leonard and Penny are having a Halloween party in their apartment and Howard and Bernadette are dressed up as Bert and Mary Poppins.
  • Raj was dressed up as Ruth Bader Ginsburg and Anu dressed like the U.S. Constitution.
  • Penny did remember their first kiss, but she wanted to forget about that day, it wasn't a good day when she was dating Kurt. Leonard understood.
  • This episode was released on the 40th anniversary of John Carpenter's Halloween.


Leonard: Oh, my God, you look amazing.
Raj: I find you guilty of murder, because you are killing it.
Howard: (imitating Sheldon) Well, technically, the Supreme Court wouldn't determine a defendant's guilt or innocence in a criminal matter. They could only reverse or revamp a jury's conviction based on a constitutional or statutory issue.

Sheldon: Amy, do you think I'm always correcting other people?
Amy: No, not all the time. I mean, just last week, Penny ended a sentence with a preposition. You didn't even mention it.
Sheldon: True. I just waited until I got home and screamed into a pillow.

Penny: No, it does matter. Okay? You were right. It was Halloween. I was dressed as a cat, you were a hobbit. It was right there on that couch.
Leonard: Why didn't you just say that?
Penny: Because I always hated that was our first kiss. I was drunk, and I was still with Kurt, and I was using you to make myself feel better. I just wanted our first kiss to mean something. That's why I said it was the one on your birthday.
Leonard: I like that. We'll make that our official first kiss.

Bernadette: She's not. It's been happening my whole life. And-and she called me out for being mean? Well, I've had to be mean. It's hard to be taken seriously when you're always the smallest person in the room.
Sheldon: I know that. I was in high school when I was nine years old. I tried to tell the other kids that although my physical stature was small, my intellectual stature towered over them. That only seemed to make things worse.

Raj: Hey, did you guys know this year's the 40th anniversary of Halloween?
Sheldon: Oh, nonsense. Halloween traditions date back to the Celtic festival of Samhain. Although our current Halloween customs come from the evening before All Hallows' Day, All Hallows' Eve. Thus, Halloween.
Raj: I meant the movie Halloween.
Sheldon: Oh. Well, that's not interesting at all.
Leonard: Did you know the Michael Myers mask from the film was actually a Captain Kirk mask turned inside out?
Sheldon: Okay, now it's interesting.

Howard: Hello. [dressed like Sheldon, imitating him]
Sheldon: Hello.
Howard: I see you are dressed as Doc Brown from Back to the Future. May I assume that Amy is going as his wife, Clara Clayton, from Back to the Future Part III?
Sheldon: Yes. Looking good. [referring to Howard's outfit as he is dressed as Sheldon]

Sheldon: Well, I can understand how that would make someone irritable.
Howard: Interesting fact: "irritable" comes from the Latin, "susceptible to anger."
Sheldon: Just because I used a word doesn't mean I want its etymology.
Howard: Interesting fact: "etymology" comes from the Greek word-

Amy: Hey, why aren't you in your costume?
Sheldon: I just didn't feel like it.
Amy: You get that I'm wearing a corset because of you, not because I'm tired of breathing?

Leonard: Hey, do you remember what happened at that first Halloween party that you invited me to?
Penny: When I threw up in the pumpkin?
Leonard: More memorable than that.
Penny: Really? That was pretty impressive.
Leonard: We had our first kiss. On this very couch.
Penny: No, no, our first kiss was at your birthday. Remember? I threw you a party, you didn't make it, and I felt bad for you.
Leonard: No, no, it was on Halloween, and you felt bad for me.
Penny: If we're gonna go through every party where I felt bad for you, we're gonna be here awhile.

Bernadette: How many times has he made fun of Howard for being an engineer? Going to MIT? His magic?
Amy: Sheldon doesn't make fun of his magic.
Bernadette: Well, he should. It's stupid.

Howard: (imitating Dick Van Dyke's cockney accent) Well, Gorblimey. You look like a thousand tuppence. Don't he, Mary Poppins?
Bert: Are you gonna talk like that all night?
Howard: Jiff willikers, I am.
Bernadette: Isn't he cute? He's gonna get a spoonful of sugar later.
Howard: And I'm gonna sweep Ms. Poppins' chimney.

Amy: (imitating Bernadette) Happy Halloween.
Sheldon: Who wants to see a magic trick? Oh, that's right. No one.
Bert: Ha! They're you.

Bernadette: What do you think you're doing?
Amy: I thought it was clear. I'm being unnecessarily hurtful but with a sweet voice.
Sheldon: And I don't understand what's going on because I went to MIT.

Sheldon: I think Howard hurting my feelings has in some ways made me a better person.
Amy: Hmm. Look at you, improving on perfection. How so?
Sheldon: As you were eating that Danish, I wanted to point out that the Danish isn't Danish at all. It was imported by Austrian bakers during a labor dispute in the 1800s. But I chose not to, because I didn't want to be the kind of fella who foists unwanted facts about European pastries on the unwilling.
Amy: Huh. That's actually interesting.
Sheldon: Sorry. Now you'll never know.

Sheldon: I don't understand. If it's unreasonable, why should we do it?
Howard: Okay, how about this? You know in Star Wars when R2 and Chewbacca were playing holochess?
Amy: Really? Star Wars?
Sheldon: Amy, let the man speak.

Bernadette: One time my brothers made me breathe helium. I tried to call for help, but the only one who could hear me was the dog.
Sheldon: That's also terrible. My goodness, you had to live in a house with a dog.

Penny: Bernadette, why don't we get to dress up at work?
Bernadette: We used to, but a couple guys in the infectious disease lab went as zombies and it triggered a quarantine. The CDC was so mad.

Leonard: Hey, happy Halloween.
Penny: Oh! Trick or treat.
Leonard: No. Sorry, you're not wearing a costume.
Penny: Yeah, I am. I'm a pharmaceutical sales rep.
Leonard: I'm gonna need more.
Penny: Okay, failed actress who traded constant rejection for a Christmas bonus and a dental plan?
Leonard: Go nuts.
Penny: Oh. I will.

Leonard: So, what are you wearing to the party? Sexy cat? Sexy nurse? Sexy zombie?
Penny: Why do girls' costumes have to be sexy but guys' costumes don't?
Leonard: (scoffs) Say that again with this helicopter on my head.
Penny: Very cute.

Leonard: Oh, that's great. He's a Supreme Court justice, and you're the U.S. Constitution.
Anu: Yep. He interprets me. And guess what's underneath this? The Bill of Tights.

Bert: All right, I'll tell you. I'm Maurice "Doc" Ewing, winner of the 1960 Vetlesen Prize, generally regarded as the Nobel Prize of geology.
Bernadette: Oh, yeah. Now I see it.
Bert: Ask me how I died. Spoiler alert: brain hemorrhage.

Leonard: So, here we are. On Halloween. On this couch. Does it ring any bells?
Penny: Really? We're still doing this?
Leonard: I'm just surprised you don't remember our first kiss.
Penny: (sighs) Fine. It was on Halloween.
Leonard: Are you agreeing just to shut me up?
Penny: You got another way? I'm all ears.

Howard: You know what, guys? You got us. Congratulations. Now why don't you go back to your apartment and put on your other costumes.
Amy: Oh, but it's so far away, and I have such teeny, tiny legs.

Bernadette: Can't believe Amy did that.
Howard: Oh, come on. You thought it was funny when I dressed up as Sheldon.
Bernadette: That was totally different.
Howard: How?
Bernadette: That didn't hurt my feelings.

Bernadette: The kids called me Bernadette the marionette.
Sheldon: (laughs) Because you're small. That's funny.
Bernadette: No, it's not.