Recaps for all the episodes in Season 5.

Episode 01: The Skank Reflex Analysis
The series picks up hours after the season finale where Penny emerges from Leonard’s room, with Raj right behind her, saying “This isn’t what it looks like.” Sheldon is working through her cryptic statement and trying to figure out what it actually WAS. Annoyed, Leonard finally tells him that it was exactly what it looked like – Penny and Raj slept together. When the four boys reunite in the cafeteria, tensions run high as Leonard is upset with Raj and doesn’t understand how he could do that to him. When Raj confesses that he and Penny are in love, Leonard scoffs and tells him that he was in love with Bernadette just months before. Howard is shocked at hearing this and the three boys start arguing. Sheldon tries to get them to discuss more important matters, like the upcoming paintball tournament. Meanwhile, Penny is distraught over sleeping with Raj and Amy comes over to comfort her. Penny can’t take being in the apartment anymore and goes to stay with Amy. Penny starts questioning her entire life. Everything sucks. She’s ruined things with friends. Her acting career sucks – she can’t even get the hemorrhoid commercial she auditioned for last week. Koothrappali comes over to Amy’s to ask Penny out. She breaks it to him what they did was a huge mistake. Penny says she just wants everything the way it used to be. He reveals they actually didn’t have sex in the conventional sense…he tried to put the condom on and she tried to help him but nothing more happened after that. He still thinks it was a beautiful experience but asks her not to tell anyone about it because he’s a bit embarrassed. She reluctantly agrees. The guys are at the paint ball game but Leonard, Raj and Howard are too upset with each to even care about playing. Sheldon takes it upon himself to inspire his troops and commits “suicide” but running out into the game without his gun. The three guys, inspiried by his matrydom, run out to avenge Sheldon’s death. Back at the apartment, Penny joins the guys who’ve basically forgiven each other. She tells them she’s decided to move back to Nebraska because her life in California hasn’t amounted to anything. While Leonard tries to convince her otherwise, Penny gets a call from her agent, informing her that she booked the hemmorhoid commercial. Penny, inspired again, abandons the idea of leaving. The guys are left with their friend still living across the hall and Raj bragging about how he slept with her.

Episode 02: The Infestation Hypothesis
­Priya returns to India but Leonard and her agree to try a long distance relationship. The video chat daily and Leonard, trying to keep the spark alive, convinces Priya to try virtual sex which Leonard is not very good at. He gives it a last try, undressing in front of his monitor, talking dirty to Priya but soon Leonard realizes Priya is not the one on the other end of the video chat – it’s her parents. Leonard annoyed at Leonard video chatting with Priya heads to Penny’s apartment and is happy to find a new comfortable chair. When Penny tells him she found it on the street he is horrified to think of all the germs that have infested it and that are now on his body – he demands for Penny to get rid of it but she refuses. Sheldon enlists Amy’s help to convince Penny to throw away the chair while Sheldon is freaking out that he has lice crawling all over his body. Amy gives it a try but Penny catches on to Sheldon’s game and tells Amy to leave. Amy fearing she is about to lose her “bestie” takes back everything she just said and tells Penny she loves the chair. Amy sits down on it and both are shocked when a rat that was hiding in the chair jumps out to bit Amy. Penny begs Amy to never tell Sheldon what happened.

Episode 03: The Pulled Groin Extrapolation
With Bernadette, Howard and Raj going to the movies, Penny going to work and Sheldon getting a ride from one of those groups to the train store, Leonard finds himself alone in the apartment with Amy. At first, Leonard is ill at ease with Amy being there, but soon, he grows comfortable with her presence and her contendedness to just sit. Sheldon returns from the train store to find Amy still in the apartment. She tells him that she’s rescinding her invitation to accompany her to a wedding that weekend and instead, Leonard is going to be her date. Meanwhile, Bernadette gets a surprise when Howard talks about how the two of them are going to move in with his mother once they’re married. They get into a fight but he soon convinces her to just spend the weekend with them to try it out. Bernadette agrees and soon Howard discovers that he might be marrying a too-close-for-comfort version of his mother. At the wedding, Amy takes Leonard totask for always being a sad sack. She convinces him to dance with her and he finally agrees. They have a great time and Leonard gets so enthusiastic that he tries to do the splits, thus straining his groin. It doesn’t damper his good time and at the end of the night, Leonard thanks Amy and kisses her on the cheek. Amy immediately goes to Penny and tells that she unwittingly made Leonard fall in love with her. When Leonard tells Sheldon that he and Amy had a good time and she’s a lot of fun, Sheldon immediately karate chops Leonard in the neck, exclaiming, “She’s not for you!” Sheldon gets territorial. About a girl.

Episode 04: The Wiggly Finger Catalyst
­Penny sets Raj up with a deaf girlfriend of hers, solving his problem of talking in front of a woman, and Raj falls for her instantly. He showers her with lavish gifts until his parents soon cut him off and Raj discovers love is not enough for her when she dumps him.

Episode 05: The Russian Rocket Reaction
Sheldon and Leonard run into Wil Wheaton at the comic book store. Wil invites them to a housewarming party. Leonard says he’s actually thinking of going. Sheldon tells Leonard he would be betraying his trust and friendship if he went because Wil Wheaton is one of Sheldon’s mortal enemies. Sheldon further explains that, until Leonard makes a decision about the party, Sheldon is simultaneously his friend and NOT his friend. Sheldon calls this phenomenon, “Schrodinger’s Friendship.” Wolowitz shows up at Leonard and Sheldon’s apartment with big news: He’s going to be an astronaut! Well, sort of. NASA picked his team’s design for a piece of equipment that will be installed on the International Space Station. Someone has to go up with the equipment as a Mission Specialist and as it stands, Wolowitz is the standby backup. Bernadette expresses her concern – going into space is dangerous, plus Wolowitz would have to take an old Russian, Soyuz rocket to get to the space station. Later, Wolowitz is upset that he doesn’t have Bernadette’s support for his big dream. Once the guys get to Wil Wheaton’s party, Wil has a surprise for Sheldon. He gives him an autographed, one sixty-fourth scale mint-in-package Wesley Crusher action figure. He even wrote, “To Sheldon, sorry this took so long. Your friend, Wil Wheaton.” Sheldon is so excited that he shows the box to Brent Spiner. Unfortunately for Sheldon, Brent Spiner rips the package open. This immediately lands Brent on Sheldon’s list of mortal enemies.

Episode 06: The Rhinitis Revelation
Sheldon’s mother, Mary, comes to visit and the entire gang loves spending time with her, much to Sheldon’s chagrin. He refuses to believe it’s jealousy but, when he comes down with the common cold like a “common man”, he’s gleeful that mommy is there to take care of him and sing him “Soft Kitty.”  

Episode 07: The Good Guy Fluctuation
Leonard meets a really cool girl, Alice, in the comic book store who immediately expresses an interest in him. The more time he spends with her, the more conflicted he feels about his relationship with Priya. In the end, he confesses to Priya that all he and Alice did was kiss and it will never happen again but Priya tells him she also messed up by sleeping with her ex-boyfriend. They both agree that perhaps the long-distance thing isn’t working out so well. In honor of Halloween, the guys pull pranks on Sheldon throughout the episde. He tries to retaliate but they always seem one step ahead. 

Episode 08: The Isolation Permutation
Amy is heartbroken when she learns Penny and Bernadette went to look at bridesmaids dresses without her. Sheldon is having trouble getting in contact with Amy, so Leonard drives him over to check on her. They find Amy sadly playing “Everybody Hurts” on the harp. Amy explains that she’s sad because Penny and Bernadette went shopping for bridesmaid’s dresses without her. Sheldon asks her what he can do to help and she says, “comfort me.” She then tells him she craves human intimacy and physical contact. When Sheldon reminds her that theirs is a “relationship of the mind,” Amy suggests that maybe one night of passion might blot the pain. Sheldon instead offers to stroke her head for five minutes or until she falls asleep – whichever happens first. Wolowitz tells Penny and Bernadette what happened with Amy and they tell him that Amy has just been taking her bridesmaid duties to an extreme but go to apologize — Amy doesn’t accept. Later, Amy calls Sheldon drunk and Sheldon blames Leonard for Amy’s behavior since he brought Penny into the group. In the end, Bernadette tells Amy she wants her to be her made of honor and Amy enthusiantically accepts, taking out her video camera to capture the moment. 

Episode 09: The Ornithophobia Diffusion
Leonard and Penny try to hang out alone as friends for the first time since they broke up. Sheldon’s phobias are put to the test when a bird camps out on the living room window sill. 

Episode 10: The Flaming Spittoon Acquisition
When Stuart asks Amy out on a date, Sheldon finds himself jealous. Everyone is shocked when Sheldon officially asks her to be his girlfriend. 

Episode 11: The Speckerman Recurrence
­When Leonard is contacted by a former high school bully through Facebook, he cringes at the memories. The former classmate is going through some rough times and reaches out to Leonard, not realizing that he had made Leonard’s life hell. Leonard agrees to meet with his former bully and the guys decide to accompany him for support. When Leonard confronts him about how mean he was, the guy feels badly and goes into a depression, making Leonard feel guilty. In the meantime, Amy and Bernadette help Penny choose a philanthropic endeavor. 

Episode 12: The Shiny Trinket Maneuver
­Amy gets professional recognition and Sheldon, in his self-centered way, couldn’t care less. Penny, Koothrappali and Leonard go about trying to make Sheldon a better boyfriend by getting him to realize that sometimes in a relationship you need to pretend to care – even when you really don’t. At the same time, Wolowitz and Bernadette realize they need to discuss their feelings about children, after Howard performs a magic show at his nephew’s birthday party with Bernie as his assistant. We learn Bernadette can’t stand being around kids.  

Episode 13: The Recombination Hypothesis
­Leonard decides to ask Penny out on a date, and they both agree to give their relationship another chance. They argue over dinner and remember why they didn’t work in the first place, but they end up sleeping together afterwards anyway. They agree to secretly continue seeing each other under the condition that they act like friends around everyone else, just so that they can make sure the relationship works. Eventually it is revealed that this is just a fantasy for Leonard, but it does inspire him to actually ask Penny out. She agrees to go to dinner with him, and their relationship begins anew. 

Episode 14: The Beta Test Initiation
­Leonard and Penny decide to put their relationship through a ‘beta test,’ which allows them to report the problems they have with each other as ‘bugs,’ like a programmer would do with computer software. When they exchange lengthy lists of relationship bugs, Leonard takes it to heart and decides to take Penny to on a real date to a gun range, where he promptly shoots himself in the foot. Meanwhile, Koothrappali buys an iPhone 4s from the mall and falls in love with Siri. Wolowitz and Bernadette become concerned when he starts treating his phone like a real woman. Sheldon and Amy try to achieve internet fame by creating “Sheldon Cooper Presents: Fun with Flags,” a video podcast dedicated to the study of flags. 

Episode 15: The Friendship Contraction
After Sheldon keeps Leonard up all night with an natural disaster drill, Leonard decides that he needs a break from taking care of Sheldon. Hurt, Sheldon invokes clause two-oh-nine of their Roommate Agreement, which minimizes their interaction and ‘legally’ ends their friendship. After a while, Leonard starts to feel bad for Sheldon because he has no idea how to take care of himself on his own. Sheldon proposes they celebrate ‘Leonard’s Day’ once a year to celebrate all of Leonard’s contributions to his life, and Leonard then agrees to reinstate the Roommate Agreement. Meanwhile, Wolowitz is preparing to go on a flight to the International Space Station, and he notices that all of his crew mates have cool astronaut names. He enlists Koothrappali to help him subliminally plant the name ‘Rocket Man’ into his crew mates’ minds, but their plan fails and his crew code name becomes Fruit Loops.  

Episode 16: The Vacation Solution
Sheldon is forced to use his two weeks of vacation time from work, so he goes to work with Amy in her biology lab. He feels the tasks she asks him to do are menial and boring, but when she finally relents and asks him to dissect a brain, he cuts his thumb and passes out from the pressure. Bernadette wants Wolowitz to sign a pre-nup before their wedding, so Penny asks Leonard to try and get his feelings on the subject. 

Episode 17: The Rothman Disintegration
Sheldon and Kripke argue over who should get Professor Rothman’s vacated corner office, so Leonard, Koothrappali, and Wolowitz devise a contest for them which awards the office to the winner. Unfortunately, the contest centers around a subject which Sheldon and Kripke are equally terrible: sports. Meanwhile, Amy buys Penny a garish painting as a gift to celebrate their friendship, but Penny hates it. She and Bernadette struggle to come up with ideas for how to discreetly dispose of the painting. 

Episode 18: The Werewolf Transformation
Sheldon’s routine world is turned upside down when he learns that his longtime barber passed away, so he tries to act like a hippy to match his new shaggy hairstyle. Meanwhile, Wolowitz is sent to Houston for the grueling NASA training program, and he shares his horrific stories with Bernadette via Skype.