Penny worries that her behavior has screwed things up permanently with her friends. Meanwhile, Sheldon takes command of their paintball team, but the guys are too worried about their own personal problems to take it seriously.
Extended PlotThe episode starts just a couple of hours after the previous season 4 episode, with Sheldon trying to solve a "puzzle" presented by what Penny said in the last episode ("It's not what it looks like."). He comes to the conclusion that Penny was checking Raj's anal region for pinworms because of what it looked like to him and because Raj is from India; a third-world country, greatly disgusting Leonard. Leonard then clarifies that Raj and Penny did have sex and she lied.
Howard and an embarrassed Raj arrive and Sheldon informs them about the University's interdepartmental Paintball Tournament. He asks Leonard if the situation is awkward because Raj had just slept with Penny in Leonard's own bed. After Leonard sarcastically answers that he's fine with it, Sheldon answers that he knows it's sarcasm but doesn't care. Sheldon then begins to ponder about his rank within his team. However, this is the last thing on the other guys' minds, and Leonard and Howard quickly gang up on Raj, angrily asking him how he could sleep with Penny. Raj, however, believes that Howard and Leonard are angry that he was Penny's second choice after Leonard, and this encounter means that he and Penny are in love and have a relationship. Leonard counters this by claiming that Sheldon would even go before Raj, and that Raj falls in love with every girl that smiles at him, and just over a month ago, had been writing poems about Bernadette (which he had learned about from Pryia in the previous season), exposing Raj's feeling about Bernadette (much to Howard's shock). When Raj tried to claim that this is rubbish, Leonard recites part of one of the poems that is innapropriately worded (Oh Bernadette, please play my clarinet!) apparently upsetting Howard even more.Sheldon then interrupts to declare that his rank would be captain.Later, Penny grabs some wine and can't find a glass, so she improvises and uses a measuring cup instead.
Amy arrives, observes Penny drinking wine out of a measuring cup and comments about it being good that that she is measuring her intake of wine; saying that she knows that Penny had sexual relations with Raj. Just as they are about to exit the apartment they bump into Leonard and Sheldon. Penny then slams the door with a pained expression on her face. Penny asks Amy if she can sleep at her apartment for a while and Amy delightfully welcomes her, exclaiming about how she can finally experience a traditional girls' sleepover.
At their apartment, Leonard is showing Sheldon his camouflage suit for the Paintball Tournament which he cites as unnecessary, while Sheldon pretends the camouflage is extremely effective. Sheldon has called up Leonard's mother, Beverly Hofstadter, to console Leonard. After Leonard tells her his troubles, her sole piece of advice is an unhelpful "Buck up, sissy-pants."
Later, Raj is seen drinking beer in his apartment, just as an angry Bernadette bursts in knowing about Raj's feeling about her after being told by Howard, who was completely freaking out. Raj asks her if he has a shot with Penny, to which Bernadette reassures him that he does (although still in quite an angry voice).Back at Amy's apartment, Amy is combing Penny's hair, following girl's sleepover tradition. Raj enters, and Amy leaves them alone. Raj then asks Penny to go on a date. Penny says that she had intercourse with Raj purely because she was drunk. She tells him that she wants to go back the way they were - as friends, which Raj accepts. Before they end the discussion, he claims to her that they didn't have sex in the "conventional sense." Penny gets the wrong idea and angrily asks him if he pulled some weird "Indian crap" on her. Raj claims to Penny that when they were about to have sex, Raj was having hard time putting on the condom, he had an "early" start when Penny helped put it on, and they both fell asleep naked, but in reality, they both had no memory of what really happened because they were drunk. Penny is both shocked and relieved by this claimed admission, but agrees to not tell the others.
As the boys are discussing strategies in a paintball shack, Sheldon shows an overhead display of the paintball field via Google Earth and explains his plan to take out the Geology Department. Leonard, Howard, and Raj are not in the mood to play paintball. Sheldon blames himself for his team's lack of motivation and tries to rip off the Captain insignia he had sewn on, but he is unable to do so.
Sheldon begins to exit the shack, and when Leonard asks him where is he going, Sheldon replies that he is "following the footsteps of Kirk, Crunch and Kangaroo." Sheldon leaves the shack, stands in the open and provokes the enemy by saying "Geology isn't a real science!", in turn sacrificing himself, and is shot at least 20 times. Angered, Sheldon's team attacks the enemy and emerges victorious.
Back at the apartment, the boys are celebrating their victory and toast their Captain, who has, with his last breath, awarded himself a battlefield promotion to Major Sheldon Cooper. Penny enters the apartment, proclaiming that she is going back to Nebraska because her acting career is failing - at that exact moment, her agent calls her, telling her that she got a part in a commercial for hemorrhoid cream. In the final scene, the gang watches the poorly acted commercial in which Penny stars.
- Guest starring:
- Teleplay: Chuck Lorre, Bill Prady & Steven Molaro
- Story: Eric Kaplan, Maria Ferrari & Anthony Del Broccolo
- The TV Critic: "We don't really understand how Penny and Leonard see one another with much depth. We don't really understand Raj's feelings beyond him being a bit sad and lonely but with an edge of jerk to make him funny. That story has so little emotional resonance because we spent our time on the cameos. Similarly, I don't know if Sheldon really had a master plan to win the paintball game...That story has so little emotional resonance because we spent our time on the cameos... A new season, but very much the same show." 
- The A.V. Club gave this episode a B+
- IMDB user reviews
- Title Reference: Amy refers to Penny's incident with Raj as "The Skank Reflex," which is, according to her, what neurobiologists call promiscuous behavior.
- Chuck Lorre's vanity card; however, the joke was originally written by Kevin L. Schwartz in 2002
- This episode was watched by 14.30 million people with a rating of 4.9 (adults 18-49).
- This episode aired in Canada on September 22, 2011 with 3.718 million viewers and a weekly ranking of #3.
- In the United Kingdom, this episode aired on on November 3, 2011 with 1.339 million total viewers and a weekly ranking of #13
- In Australia, it aired on October 10, 2011 with 1.505 million viewers and a weekly ranking of #11.
- Episode transcript 
- Sheldon sports his ManBot t-shirt, arguably his favorite as it is the one he has worn in more episodes than any other - and in more colors (green, blue, and purple). He also wears his Flash distressed athletic jersey tee.
- Leonard is seen in a "Lunar Cycles" t-shirt from Urban Outfitters (discontinued) and a Little Timmy Robot t-shirt from Karl Addison (discontinued).
- Bernadette is only seen with one speaking scene with in this episode (The scene where she is gigantically furious with Raj) and she has a small one-second silent appearance with the rest of the gang watching Penny's commercial at the end of this episode.
- This show is the third of five episodes to have a "Previously on The Big Bang Theory" review of past events. It includes clips from "The Herb Garden Germination" (S4E20) and "The Roommate Transmogrification" (S4E24), and it is narrated by Johnny Galecki.
- In this episode, ironically, it is Leonard who reveals Raj's "love" to Bernadette to Howard, causing a turmoil among Howard, Bernadette and Raj, since previously in "The Herb Garden Germination" (S4E20) Leonard told Penny, "Well, the point is, if this got out, it would destroy Howard and Raj's friendship." Leonard also cites Raj's poem "O Bernadette, please play my clarinet", which was also first referred in that episode. This narration was used throughout the remainder of the series to remind the viewers of past events.
- Sheldon and Beverly Hofstadter think Leonard likes to point out the obvious since he was a toddler.
- Beverly has written books about parenting, which are (not in real life) available on Amazon.com.
- Sheldon thinks he follows in the footsteps of Captains Kirk, Crunch and Kangaroo.
- Amy has a secret language, which she dubs "Op." In the language she spells out every word (except for the first in a sentence) and adds 'op' to the end of each consonant. For example, instead of "sounds great," it's "sounds gop rop e a top!" It is probably a tribute to Pig Latin.
- Sheldon still takes things literally. For example, when Penny tells the guys in the season 4 final that her sleeping with Raj is "not what it looks like," he spends the rest of the morning trying to figure out what she meant. He comes to the conclusion that Penny was checking Raj's anal region for pinworms because of what it looked like to him and because Raj is from India; a third-world country. Leonard then clarifies that they did have sex and she lied.
- Howard claims Penny would've slept with him before Raj if he wasn't engaged to Bernadette. Leonard believes Sheldon would have a better chance with Penny than him.
- Penny is willing to drink wine out of anything. She thinks that after drinking wine from a measuring cup, that wine glasses should have handles. Amy mentions that is good that she is now measuring her alcoholic intake.
- When Penny is about to go out with Amy, she says she wants to go "somewhere where no one's seen me naked", and then they open the door to see Sheldon and Leonard, who both have seen her naked - Leonard in various episodes of Season 3 (when they have sex), and Sheldon in "The Adhesive Duck Deficiency" (S3E08).
- Raj is always "packing" condoms.
- This episode is the first of a three-episode whiteboard arc continued in "The Infestation Hypothesis" (S5E2) and "The Pulled Groin Extrapolation" (S5E3). The calculations on the whiteboards refer to attempts to create axions in an artificial Sun generated by focusing on 192 lasers onto a small pellet at the National Ignition Facility of Lawrence Livermore National Laboratory. As shown on the whiteboards’ Feynman diagrams, electrons in the Sun's core could produce a detectable number of axions. Axions are particles originally conceived in the late 1970′s to give a natural explanation in quantum chromodynamics of why the strong nuclear force obeys certain symmetries.
- When Sheldon falls to his knees after being shot numerous times in the paintball match he strikes the same pose as Sgt. Elias from the movie "Platoon". It is also played by Tugg Speedman (Ben Stiller) in "Topic Thunder".
- Penny lets Raj tell other people that their love burned too brightly, but not that he ruined her for white guys.
- This season premiere takes place immediately after the last episode of the previous season.
- Penny is steadily becoming an alcoholic from her guilt over the loss of Leonard.
- Leonard called Sheldon's mother twice, so Sheldon called Leonard's Mother when he thought he needed help.
- Sheldon wears the army rank of captain and at the end of the episode he promotes himself to major.
- This show is the second episode where Sheldon puts on imaginary safety equipment. The first episode was "The Euclid Alternative" (S2E5).
- Leonard calls Sheldon 'Sherlock'. Both Sheldon and Sherlock Holmes are believed to have Asperger's Syndrome, though it is unlikely since they don't enough of the same symptoms to be diagnosed as such.
- During Penny and Amy's sleepover, Penny says that she "hasn't gotten a single acting job since [she] moved out [to L.A.]". In "The Hofstadter Insufficiency" (S7E1), we learn that this is actually not true. Shortly after she moved to L.A., she had a part in "Serial Ape-ist".
- Amy's made up language Ubu Dubbiis revisited in "The Veracity Elasticity".
- Leonard: (After Howard claims Penny would've slept with him instead of Raj) Please! Sheldon would've been before you, and he might not even have genitals!
- (One minute later, after much conversation)
- Sheldon: For the record, I do have genitals. They’re functional and aesthetically pleasing.
- Penny: (looking for a glass to pour some wine, settles on a measuring cup) Yep. That's good. Wine glasses should have handles.
- Amy: Keeping accurate track or your alcohol intake. Smart idea considering how trampy you get when you've had a few.
- Penny: You heard, what I did?
- Amy: Well, I heard who you did.
- (The scene of a knock on Raj's apartment door when Raj finishes his quick sip of beer, gets up from his desk sighing to himself and opens the door to see Bernadette, who is immediately furious at him with an enormous amount of anger for confessing his fleeting feelings for her to Howard)
- Bernadette: (She is so totally furious) You jerk face!
- (Raj runs backwards nervously whilst Bernadette immediately yells at him with massive fury)
- Bernadette: What did you tell Howard? Did you say there was something going on between us? Because he thinks there is! He’s completely freaking out!
- Raj: Please, come in.
- Bernadette: (she asks a question to Raj with huge violent anger) What the hell is wrong with you?!
- Raj: You were always so nice to me; I thought maybe you liked me.
- Bernadette: (she yells with a big blast of gigantic rage) I’M NICE TO EVERYONE!
- Raj: I'm sorry.
- Bernadette: (she's still extremely furious) Damn right, you’re sorry! (she is just about to exit and then stops to yell at Raj with more enormous fury) And you tell Howard there’s never been anything between us!
- Raj: I will. Hey, Bernadette?
- Bernadette: (she's asking Raj with another huge yell of fury) What?!
- Raj: Do you think I have a shot with Penny?
- Bernadette: (she shouts really loudly with rage for one last second) Of course you do! You’re a cutie pie! Any girl would be lucky to have you!
- (Bernadette suddenly leaves in a huff and slams the door. Then the scene ends with a loud sound of door slamming while Raj puts on a reacting smile).
- Penny: You know I've done this before. In kindergarten, I was supposed to marry Jason Saridson at recess, by the time my class got out there, he was already engaged to Chelsea Himmelfarb. What did I do? Hung upside down from the monkey bars, let all the boys see my underpants.
- Amy: You can't blame yourself. When your prefrontal cortex fails to make you happy, promiscuity rewards you with the needed flood of dopamine. We neurobiologists refer to this as the "skank reflex."
- Amy: (After finding Raj at her door while Penny staying with her) A guest in my trundle bed and a boy at my door? I wish I could tell 13-year-old me, it does get better!
- Penny: We should have never slept together. It's what ruins friendships.
- Raj: You can't ruin a friendship with sex. That's like trying to ruin ice cream with chocolate sprinkles.
- Raj: (To Penny, after confessing that they didn't have sex) Can I say I ruined you for white men?
- Sheldon: (During a paintball game against the Geology Department) Geology isn't a real science!
- Sheldon: Penny’s brain teaser this morning. She and Koothrappali emerge from your bedroom. She is disheveled, and Raj is dressed only in a sheet. The sole clue, it’s not what it looks like.
- Leonard: Just let it go, Sheldon.
- Sheldon: If I could, I would, but I can’t, so I shan't. Now, knowing Penny, the obvious answer is, they engaged in coitus. But, since that’s what it looked like, we can rule that out. Let’s put on our thinking cap, shall we? (Mimes doing so) Raj is from India, a tropical country. Third World hygiene. Parasitic infections are common, such as pinworms. Mm-hmm. The procedure for diagnosing pinworms is to wait until the subject is asleep, and the worms crawl out of the rectum for air. (Leonard spits out food) Yes, just like that. Penny could have been inspecting Raj’s anal region for parasites. Oh, boy. That’s a true blue friend.
- Leonard: SHE LIED.
- Sheldon: Oh. Well don't I look stupid wearing this.(Mimes taking thinking cap off)
- Sheldon: If there's ever a church of Sheldon, this will be when it started.
- Sandy: (Penny's commercial) How are you doing?
- Penny: Sittin' pretty.
- ↑ The Big Bang Theory - The Skank Reflex Analysis (TV Episode 2011) - IMDb
- ↑ The TV Critic's Review
- ↑ The Big Bang Theory: “The Skank Reflex Analysis”/“The Infestation Hypothesis” - TV Club - The A.V. Club
- ↑ Kevin L. Schwartz's livejournal
- ↑ Thursday Finals: 'Big Bang Theory,' 'The X Factor,' 'Parks & Recreation' and 'Whitney' Adjusted Up - Zap2it
- ↑ Top Programs – Total Canada (English) September 19 – September 25, 2011 - BBM Canada
- ↑ BARB via wikipedia
- ↑ ABC's Doc Martin beats Nine, TEN's best all week. - TV Tonight
|Episodes | Season 5|