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The Maternal Combustion

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Not to be confused with The Maternal Capacitance or The Maternal Congruence.

"The Maternal Combustion" is the twenty-third episode and penultimate episode of the eighth season of the American sitcom The Big Bang Theory. The episode aired on Thursday, April 30, 2015.


While both Sheldon and Leonard's mothers visit to see their sons get an award, Bernadette wants more help around their new home from RajHoward and Stuart.

Extended Plot

While setting up dinner, Leonard, Sheldon, Penny and Amy are discussing the upcoming the visits of the guys' mothers to see them get an award. Leonard knows when his mother reaches California airspace by feeling a disturbance in the Force. Sheldon is preparing a bowl of yellow roses for his mother. If Amy asks for roses, then he calls them a "bouquet of severed plant genitals". Sheldon did get her a rotting log that produced mushrooms for Valentine's Day. Penny wonders if she should get something for Beverly since she is not that excited about her relationship with Leonard. Leonard suggests her getting a Ph.D overnight, though Penny points out that it did not work for him and his mother. Will the two different women get along? One is brilliant while the other is sweet and simple according to Sheldon who compares it to his relationship with Leonard, much to Leonard's chagrin.

Sheldon is having tea with his mother who is proud of both of the, but can't understand the research paper they wrote about understanding the universe as an n-dimensional super-fluid. And the God saving the world with an ark is nonsense? Sheldon wants his mother to keep the Bible babble down when talking to the brilliant psychiatrist and woman of science Dr. Beverly Hofstadter. Mary wants to know if Sheldon is ashamed of her. Sheldon does love her, but is embarrassed by the things that she believes, does and says.

Oh kay.

Leonard and his mother are climbing the stairs, while she asks about a wedding date. Leonard and Penny are taking it slow. "I see," comments Beverly. After seeing each other for seven years, she wonders if the sex between them is satisfactory. Leonard reluctantly agrees. "Only satisfactory?" Leonard changes his answer to that it's very hot and then Beverly wonders why he is trying to impress his mother with his sexual prowess. Leonard then asks his mother not to do all her analysis in front of the sweet religious Mary Cooper. Beverly assures him that she knows how to address other people's walks of life, until she finds out that Mary is from East Texas.

Enter the apartment, Sheldon goes to greet Beverly who read their paper and called it brilliant. She didn't say anything to Leonard. She feels that is a mother's job to make sure that her child's self-esteem is not dependent on any else's approval, to which Leonard laughs at the idea that his mother thinks he has self-esteem. Mary and Beverly meet and shake hands. Both had good flights, though Mary felt like someone, she's not saying who, was watching over her. Beverly asks if she was kidding. Leonard then tells his mother "Subtle, Mom. Real subtle.".

In her house, Bernadette comes into the kitchen and finds Stuart in his underwear taking care of an itch on his posterior. Bernadette doesn't mind him living there, but among the rules, he has to wear pants. Howard then enters the kitchen in only underwear and socks.

Lazing about playing video games!

Mary tells Beverly that she must be very proud of her son. She replies that he is arguing his first legal case in front of the Supreme Court. "He did?" asks Mary. Oh, you mean Leonard?, says Beverly. A moment of silence, she says in apparently unconvincing tone "Yeah, he's terrific.". Sheldon starts to show Beverly the math he worked out for his hypothesis. Oops, Leonard's hypothesis. Beverly wonders when Mary first knew that Sheldon was going to have such a remarkable mind. When he was thirteen he tried to build the nuclear reactor to supply electricity for the whole town because he was always concerned about the well-being of others. This statement confuses Leonard. To power the reactor he had arranged to get some yellow cake (uranium) from a warlord in Chad (Africa), his mother thought he was getting some Twinkies from a local friends. Leonard wants his mother to tell the story about how he made a Van de Graff generator out of their vacuum cleaner. Beverly just stupidly comments that he broke the vacuum cleaner.

Howard and Raj are playing a video game in the living room, while Stuart is reading a magazine and wearing pants. Bernadette returns after doing a lot of errands of washing the car, picking up cleaning supplies and going to the bank and declares that she is going to stop being the mother of three lazy teenagers. She wants them to clean the kitchen from top to bottom including Raj who is doing his laundry at their house. 

Sheldon is showing Beverly pictures of when he got his bachelor of science degree. Sheldon doesn't look happy because he just began puberty. Mary says that Shelly does not like change. Penny pops in the door and apologizes that she got caught up at work. She rushes over and hugs Beverly who says, "Oh, okay." Hugging Mary she gets a much sweeter greeting. Penny shows off her engagement ring that Sheldon announces was made from a re-purposed diamond drill bit. Leonard denies that and then wants to talk to Sheldon alone. Leonard tells Penny that it came from Tiffany's, though Sheldon is sure that only the box came from that store, but Leonard crossly orders him to keep walking. Penny doesn't care how much Leonard spent on the ring, she thinks.

In Sheldon's room, he wonders if he misspoke abut the ring. Leonard feels that Sheldon is hogging the attention from both mothers like a seal pup or a "Super weaner". Leonard does think he is being a super wiener. Sheldon feels that the situation is like when two mothers faun over the same pup making him a "double mother suckler", which Leonard also agrees with.

Penny admits that they aren't in any rush to set the date for the wedding. Mary tells her it doesn't matter and that the moment a woman lays with a man, they are married in the eyes of the Lord. Beverly sighs "Ugh." Mary then asks if the Bible is "ugh" to her. Beverly apologizes and says that she forgets how much a person's superstitions mean to them. Mary counters that she read Beverly's books that Sheldon sent her about superegos and ids and she wonders what bull dropped that on the barn floor. Sigmund Freud. Penny tries to get them together because they both like Jewish guys with beards. Mary tells her to stay out of this. Mary's bearded guy teaches love and compassion while Freud wants to talk about why you want to hold your poop and crawl back into your Mamma. Beverly counters asking how can someone an enlightened as Sheldon comes from someone like his mother. Beverly is not going to like the answer. While driving to church and pregnant with Shelly, she prayed that her son was smarter than his dumb-ass daddy and she saw a bobble-head of Jesus in the next car nodding yes. Beverly hits her forehead in frustration. Mary tells her to keep doing it and maybe it'll knock some sense into her head. Penny wants to change the subject to shoes or how cute tiny Chinese babies are. Leonard and Sheldon come back out with Sheldon saying that it's not his fault that Beverly likes him better than she likes Leonard. Leonard gets angry with Sheldon and angrily yells at him telling him not to flatter himself and that Beverly likes everyone better than she likes Leonard (Which doesn't make any sense because she doesn't like Howard and Raj much either). Now Penny hits herself in the head.

The Wolowitz household guys are cleaning out the kitchen. Raj is working on the refrigerator. Howard apologizes to them, but Stuart says that Bernadette does work hard around the house. Raj tells Howard that she should stop babying him like his mother did. Howard agrees and that he has to start acting like an adult in their marriage. He decides to take out the garbage. Picking up the bag, it splits, spilling the contents all over the floor.

Beverly and Sheldon are having tea in a café and Beverly apologizes for upsetting Mary. Sheldon replies her mother will forgive her since if she doesn't she'll go to hell. Beverly also mentions she can't help but notice how Mary's unconditional love for Sheldon is diametrically opposed to her own parenting style. Sheldon describes her style has doling out affection as a reward for achievement, a proven way to raise a child or train a rat. Sheldon still turned out very successful under his loving mother. Leonard's brother and sister are very successful under Beverly's style while Sheldon's brother and sister are mouth breathing idiots. Beverly asks if he would have flourished more under a reward based childhood. Sheldon answers perhaps but his mother made him spaghetti with bits of hot-dog in it whenever he wanted, so he doesn't care.

Leonard and Penny are talking to Mary as Leonard complains that he never got any love or affection from his mother for just being himself and that he always had to earn it. Mary assures him that she loved him in her own godless way and she feels bad about the Combat. Penny assures him that he doesn't have to earn her love and he knew that when he bought her that princess drill bit diamond ring. Mary plans to apologize to Beverly just like a good Christian, though a real Texan would have shot her. Then she asks them if anyone is in the mood for spaghetti and hot dogs. Leonard doesn't feel like he deserves it.

If I want roses they're "bouquet of severed plant genitals".

Howard is finished cleaning up the big sticky mess of the garbage spill. Bernadette comes in and tells them how they everything by themselves. Howard agrees, but then first his shoe and then his sock sticks to the floor.

Beverly and Mary shake hands and agree to respect each other's beliefs. And Mary will pray for her. Leonard wants to get his mother quickly back to her hotel. Beverly admits that she always made him earn his affection, but she wants to initiate a new protocol to shower him with unconditional love. When will that start? Beverly then calls him so needy. She opens her arms and asks him to come to Mommy. They have an awkward hug. Beverly: (Unemotionally) Oh my, son. Leonard: Oh, my mother. Penny: Oh, my God.

Still cleaning up the kitchen, Raj starts to whistle "It's a Hard-knock Life" from the musical Annie. They all join in singing it enthusiastically. Bernie comes in and immediately leaves without saying a word.



  • Title Reference: The title refers to the friction that occurs between Dr. Beverly Hofstadter and Mary Cooper during their mutual visit.
  • Taping date: April 14, 2015
  • This episode was watched by 13.85 million people with a rating of 3.4 (adults 18-49).
  • Total viewers including DVR users 18.54 million.
  • The Big Bang Theory was ranked #1 for the week ending 3 May 2015.
  • This episode aired in Canada on April 30, 2015 with 3.16 million viewers with a weekly ranking of #1.
  • Screened in Great Britain on E4 on Thurs 10th June 2015
  • Broadcast sixteen days after being taped. Not a record, but very quick turn around time. 
  • IMDb user reviews [1]
  • Chuck Lorre Vanity Card [2]
  • Episode transcript [3]


  • Jesse Schedeen at IGN - It was also fun to see the dynamic between Beverly and Mary steadily degenerate from polite friendliness to all-out disdain over the course of the episode. Their nonstop barrage of insults and exasperated responses was entertaining, especially with Penny caught in the middle and struggling and failing to keep the peace. It was a rivalry born out of a very natural place of misunderstanding and mistrust, which is more than can be said for some of the contrived arguments on the show...We've been waiting a long time for Leonard and Sheldon's mothers to butt heads, and this episode didn't disappoint in that area. The tension between Beverly and Mary wasn't just amusing, it shone a light on their sons' emotional woes and the challenges they face as adults.
  • IMDb user reviews [4]


  • Third consecutive episode in Season 8 where Amy only appears in one scene. Mayim Bialik took some time off to spend time with her family following her father's death. Because of this, Amy's chance to meet Leonard's mother for the first time and once again interact with Sheldon's mother throughout this episode is blown and it is not even explained in the episode where she is and why she isn't there and Mary does not even ask Sheldon about her, which is quite a plot hole.
  • Howard, Bernadette, Stuart and Raj are only seen at the Wolowitz House in this episode and they do not come to Apartment 4A to visit Leonard and Sheldon's mothers and share a scene with Leonard, Penny and Sheldon. Also, they don't share the one scene with Amy she was seen in with Penny, Sheldon and Leonard in the opening Apartment 4A scene of this episode either.
  • First physical appearance on TBBT set of Beverly since "The Maternal Congruence" (S3E11).
  • First appearance of Beverly in Pasadena since Season 3.
  • This episode aired on both Kunal Nayyar's 34th Birthday and Johnny Galecki's 40th Birthday on April 30, 2015.
  • Mary Cooper hasn't appeared in Pasadena since season 5 and hasn't seen Leonard or Penny since then. 
  • Amy only met Sheldon's mother once in Season 4's "The Zazzy Substitution" (S4E3) and that is two times she hasn't met her again in both this episode and in Season 5's "The Rhinitis Revelation" (S5E6).
  • The idea of Beverly and Mary meeting and facing off has been in the works since season 6 as revealed in interview with the writer on various occasions, but due to both actresses not being available it was postponed to this season.
  • Sheldon has prepared his mother a bowl of yellow roses, the unofficial flower of Texas as in: There's a yellow rose in Texas, that I am going to see...
  • Considering how close Amy and Sheldon are getting, it is usual that she did not sit down with Sheldon's caring mother. But this is very unlikely to happen in future episodes because Sheldon's Meemaw mentions during her first appearance in "The Meemaw Materialization" (S9E14) that Sheldon's mother is okay with Amy and it is also revealed in "The Matrimonial Momentum" (S9E1) that during Mary's nightly prayers, Amy is in them.
  • Sheldon revealed that Penny's engagement ring was made from a re-purposed diamond drill bit that they bought online. Interestingly, this also means that he knew that Leonard was going to propose to Penny, yet was still surprised (and troubled) by the engagement in the season 7 finale (S7E24: "The Status Quo Combustion")
  • Second episode where characters sing as they work. First was "The Work Song Nanocluster" (S2E18).
  • Sheldon has previously mentioned his mother's favorite dish spaghetti and hotdogs. Mary Cooper offers to fix it in this episode. Penny fixed it in "The Spaghetti Catalyst" (S3E20) and Amy fixed it in "The Launch Acceleration" (S5E23).
  • Leonard's brother Michael and their sister are mentioned for the first time since "The Maternal Congruence" (S3E11) and the "The 43 Peculiarity" (S6E8), respectively, however, they were also mentioned as 'We' in "The Santa Simulation" (S6E11) when Leonard was talking about them and their parents leaving research papers for Santa.
  • Leonard's father, Alfred, is not mentioned at all in any of the talking between Penny, the boys and the mothers.
  • We see and hear Leonard calling his mother 'Mother' once again since he didn't do so in "The Raiders Minimization" (S7E4) and in "The Status Quo Combustion" (S7E24), while in all of Beverly's other previous appearances, we've heard Leonard calling her 'Mother'.
  • Leonard says his mother likes everybody else better than she likes him, but this quote doesn't quite make sense because she only seems to like Sheldon better than anybody else, seeing as she has also annoyed and belittled Howard and Raj.
  • Amy, Bernadette and Stuart don't get seen with Leonard's mother until the next season episode of "The Celebration Experimentation" (S9E17) without a chance of speaking to her. Then in the season's penultimate episode, Beverly properly meets Amy and Bernadette and talks to them for the first time; she also sees Stuart in these two episodes, but they still don't talk until "The Conjugal Conjecture" (S10E01).


  • When Leonard hugs his mother, Beverly says 'Oh, my son.' Leonard replies 'Oh, my mother' and Penny responds with 'Oh, my God' Mary doesn't even react to the blasphemy, much less chastise Penny for it. This is completely out of character for her, a devout Christian.
  • In "The Maternal Capacitance" (S2E15), Beverly when asked if she's proud says "Why? They're not my accomplishments". In this episode when asked if she's proud she says "Oh, yes".


Penny: It's so nice, she's going to love it.
Amy: Sure, his Mom gets roses. When I want them, they're a "bouquet of severed plant genitals". 
Sheldon: You act like I didn't get that severed mushroom log on Valentine's Day.
Amy: He's right. Roses die, but a moist rotting log will pump mushrooms for two or three magical years.

Mary: You can believe that, but God filling an ark with animals two-by-two is nonsense.
Sheldon: What did they feed the lions, Mother?
Mary: The floating bodies of drowned sinners, of course.

[The scene of a not-so-happy Bernadette entering the kitchen of the Wolowitz house looking very cross. Only to see Stuart in his t-shirt, socks and boxers scratching his rear end and putting the jug back on the coffee maker]
Bernadette: [she speaks softly and firmly] Stuart.
[Stuart turns around and faces Bernadette]
Stuart: [he's greeting to her rather nervously] Morning.
Bernadette: [she gives Stuart a little firm advice] We talked about this. I don’t mind you still living here, but we got to have some rules. And rule number one is pants.
[a badly-conditioned and messy-haired Howard (wearing vest, socks and boxers) enters the kitchen scratching his tummy].
Howard: Hey.
[Then Howard scratches his rear end and reaches for the wall cupboard. Bernadette immediately gets more fed up and cross by all of this].

Beverly: You’ve been on and off with this woman for seven years and engaged for one year. One has to wonder if there’s a problem. Are you having satisfactory intercourse?
Leonard: Yes, Mother.
Beverly: Only satisfactory. I see.
Leonard: I change my answer. It-it’s amazing. It’s hot. We can barely keep our hands off each other.
Beverly: Seems odd to try and impress your mother with your sexual prowess. But then, you always did have that unresolved Oedipal complex.

Mary: You must be very proud of your son.
Beverly: Oh yes. He recently argued a case before the Supreme Court.
Mary: He did?
Beverly: Oh, you mean this son. (A distraught look is now on Beverly's face) Um, (unconvincingly) sure, he’s terrific.

Leonard: So Mom. You haven’t seen Penny since she got engaged.
Penny: Oh yeah, let me show you the ring.
Beverly: Oh, lovely. It must have been very expensive.
Sheldon: Oh no, not at all. No, we found a place online that, uh, re-purposes diamond drill bits.
Leonard: We did not. That’s not true. Can I speak to you alone for a second.
Sheldon: Oh, sure.
Leonard: It came from Tiffany’s.
Penny: Oh.
Sheldon: You mean the box, right?
Leonard: Keep walking!

Mary: The Bible is “uck” to you?
Beverly: No. I’m sorry. That was inappropriate. AS a psychiatrist I know how important people’s superstitions can be to them.

[The scene of the messy living room at the Wolowitz house where Raj and Howard (still not dressed) are playing a video game on the settee while Stuart (who is still in his t-shirt) reads a comic on the arm chair. Stuart now is now wearing pants]
Howard: I mean, for a while, everything was vampires. Now it’s all zombies. I wonder what the next monster fad will be.
Raj: We haven’t had a good invisible man in a while.
Stuart: Clearly, you’ve never seen me try to talk to a woman.
[The pretty angry Bernadette enters the messy sitting room with shopping bags and she immediately tells the guys off]
Bernadette: [she is so very cross with the guys attitude] Guys. In the time you’ve been sitting here playing video games, I got the car washed, picked up cleaning supplies and went to the bank.
Stuart: [he speaks with a nervous smile] I put on pants.
[Stuart flutters his eyes for a few seconds and faces Howard for a second]
Howard: [he grumbles to Stuart] Kiss-ass.
[Stuart now plods his head down to his comic and twitches his lips for one second]
Bernadette: [she's getting more crosser] Okay, I don’t know when I became the mother to three lazy teenagers, but it stops today. [she punishes the guys immediately] You guys are cleaning the kitchen, top to bottom.
[Bernadette now angrily slams a shopping bag down onto the couch next to Raj]
Raj: [he speaks dissapointingly] Hey, I don’t even live here.
Bernadette: [she is still very cross] Yes or no, do you have clothes in my laundry right now?
Raj: I do.
[Bernadette is now enormously cross at Raj's 'I do' comment]
Raj: [he speaks in a rather shifty way] And some of it’s wool, so dry flat if possible.
[Bernadette now continues to get even more crosser with a 'get yourselves organized right now' expression on her face].

Beverly: I can’t help but notice how her unconditional love for you is diametrically opposed to my own parenting strategies.
Sheldon: Well, you doled out affection as a reward for achievement; a proven way to raise a child. Or train a rat.

[The kitchen scene at the Wolowitz house where the three guys are cleaning the kitchen as a punishment that Bernadette had given them]
Raj: How old is this Jell-O?
Stuart: Well, it’s carrots, so gonna say very.
Howard: Sorry we have to do this.
Stuart: Bernadette’s not wrong. She does work hard around here.
Raj: Yeah, maybe it’s a good thing if she stops babying you so much.
Howard: She doesn’t baby me.
Stuart: I saw her pull you home in a wagon.
Howard: For your information, I twisted my ankle chasing the ice cream truck.
Raj: Face it, dude, Bernadette treats you the same way your mother used to, and that was not a healthy relationship.
Howard: You’re right. It’s time for me to act like an adult in this marriage. Starting with my husbandly duty of taking out the trash. Bernie, I made a mess.

Leonard: Not once did my mother ever give me any love or affection for just being myself. I always had to earn it.
Mary: Oh Leonard, I'm sure she loves you very much in her own cold godless way.
Penny: Yeah, and you certainly don’t have to earn my love.
Leonard: Thank you.
Penny: Of course you already knew that when you bought me this princess-cut drill bit.
Leonard: That’s not what it is.
Penny: I know. I know. {Whizzzz.}
Mary: When your mom gets back, I’m gonna need to apologize for the way I spoke to her.
Penny: Well, come on now, she did kind of start it.
Mary: Doesn’t matter, a good Christian would’ve turned the other cheek. On the other hand, a good Texan would’ve shot her, so, I just kind of split the difference. Hey, who’s in the mood for spaghetti and hot dogs?
Leonard: Oh, me.
Penny: Yeah, me, too.
Mary: Coming up.
Leonard: I don’t really feel I deserve it.

Beverly: There’s something I need to say to you.
Leonard: Oh really? That’s too bad.
Beverly: Leonard: I always made you earn my affection, but today I realize that there’s more than one way to raise a child.
Sheldon: I taught her that.
Beverly: Therefore I would like initiate a new protocol where I shower you with unconditional love.
Leonard: Wow. When does that start?
Beverly: So needy. (Holding out her arms) Come to Mommy.
Penny: It’s okay. Go ahead.
(Awkward hug)
Beverly: (Unemotionally) Oh, my son.
Leonard: Oh, my mother.
Penny: Oh, my God.

Beverly: Mary, I am curious. When did you first realize that your son had such a remarkable mind?
Sheldon: Oh, good question. Everybody loves stories about Sheldon Cooper, boy genius.
Mary: Well, I’ll have to say when he was thirteen and tried to build a nuclear reactor in the tool shed.
Sheldon: Oh, this is a good one.
Mary: Now the first thing you have to know about Shelly is ever since he was a little boy he was always concerned with the well-being of others. And he didn’t think it was fair for people to pay for electricity, so he was going to power the entire town for free.
Sheldon: Tell her about the uranium. Tell her about the uranium.
Mary: Oh, well. Oh, this is adorable. When he arranged to get some yellow cake from Chad, I thought he was talking about Twinkies from one of his friends.
Sheldon: Yeah, but wasn't. ‘Cause I didn't have any friends.
Mary: No. It turns out that this scallywag was trying to use my Visa card to buy uranium from an African warlord in the country of Chad!

Mary: What bull dropped that on the barn floor?
Beverly: His name is Sigmund Freud.
Penny: Hey, look at that. You both believe in bearded Jewish guys.
Mary: Stay out of this.
Penny: Mm-hmm.
Mary: At least the bearded man that I believe in preaches love and compassion. All yours talks about is why you hold in your poop and want to crawl back inside your Mama.
Beverly: It’s fascinating. How can someone as enlightened as Sheldon come from someone like you?
Mary: I know the answer. You’re not going to like it.
Beverly: Try me.
Mary: When I was pregnant with Shelly, I was driving to church, and I was praying to the Lord to give me a son smarter than his dumb-ass Daddy. And I looked over and I saw a Jesus bobble-head in the Subaru next to me nodding yes.
Beverly: {Hits herself in the forehead.}
Mary: What is that supposed to mean?
Beverly: It means – I can’t believe were having this conversation.
Mary: Well, do it some more. Maybe you can knock some sense into yourself.

[The ending scene in the kitchen of the Wolowitz household where the three guys are doing more cleaning the kitchen and Raj starts whistling the first two lines of "It's a Hard Knock Life" for ten seconds, Howard then hums the next two lines of that tune for twelve seconds and Stuart sings the last line].
Stuart (singing): It’s a hard-knock life.
Together (singing): It’s the hard-knock life for us, it’s the hard-knock life for us. ‘Stead of treated, we get tricked, [Bernadette crossly enters, immediately turns around to exit with silent rage without saying anything at all and completely ignores their song. She has had enough of them by this point]. ‘stead of kisses, we get kicked, it’s the hard-knock life.
[The kitchen door is now closed as Bernadette is finally gone]
Howard (singing): Got no folks to...
Together (singing): speak of so it’s the hard-knock row we hoe, cotton blankets
[Raj hits the cooker, Stuart stamps his foot and Howard hits his brush on the bucket top as a beat to which they all do at the same time].
Together: (singing): ‘stead of wool, empty bellies
[Raj hits the cooker, Stuart stamps his foot and Howard hits his brush on the bucket top as another beat to which they all do at the same time again].
Together (singing): ‘stead of full, it’s a hard-knock life.



  • [5] Taping Report by Mamallama.

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