The Isolation Permutation (2011)

The girls are trying to pick out dresses for Bernadette's and Howard's wedding and seem to have trouble with it. Amy becomes heartbroken when Howard mentions a text message from Bernadette with a bridesmaid dress she likes, as she discovers that Bernadette and Penny went trying on dresses without her. Later, Sheldon tries to contact Amy numerous times using social networks like Twitter and Facebook and, after Leonard suggests it, the telephone. She does not answer to any of his messages, so Leonard takes Sheldon over to her house to check if she is okay. When they arrive at her apartment and hear her sobbing, Leonard leaves, stating that "I'm single, I don't need this crap", suggesting that he has ended his relationship with Priya . Amy tells Sheldon that she didn't answer to any of his messages because she wanted to be alone and professes how upset she is about the girls excluding her. She asks for them to engage in one night of coitus and, after bargaining over what they are going to do (including Sheldon suggesting that he pat her head and say "who's a good Amy" or a neck rub and Amy suggesting French kissing), they finally settle on cuddling. Sheldon, not liking this experience at all, tells Leonard and Howard angrily to "get their women in line" the next day, as he doesn't have time to comfort Amy and already missed the opportunity to continue his work on string theory and to start building his Lego Death Star. When the guys inform Penny and Bernadette, they feel guilty and later attempt to apologize, however Amy refuses to forgive them. That night Leonard and Sheldon pick up a drunk Amy from the parking lot of a liquor store. She tells them that she has been drinking wine to drown her sorrows, just like Penny taught her, and calls Sheldon "cuddles", much to his embarrassment. She also tries to persuade him to take her to the motel across the street and "have his way with her". They take her home, and, the next day, Penny and Bernadette try to apologize to her again. Bernadette finally succeeds by asking Amy to be her maid of honor, which she accepts full of joy because of all the wedding work to come (including Bernadette's bridal shower and bachelorette party). The episode ends with Amy taking a video of them trying on dresses together.

Title reference: Penny and Bernadette isolating Amy by going wedding dress shopping without her.