Airs Thursday, November 19, 2015.
Having badgered his other humanoid companions to no avail, Sheldon goes to the aquarium with Amy, as a friend (hence the title), during the course of which outing it is revealed Amy went on dates with 6 other men. They play a pleasant game about fish, which leads Amy to reminisce fondly about their relationship together, whilst Sheldon is thinking about the game itself. So mixed wavelengths as per norm.
Meanwhile, Howard meets Elon Musk (grand space-lord) at a Soup Kitchen, which, oddly enough, he, Raj, Bernadette and Emily are volunteering at for Thanksgiving. Elon offers to contact Howard for any future missions. This is obviously splendid news.
In another, slightly more dubious universe, Penny doesn't know when her husband's birthday is, and Leonard reads his wife's private journal. But everything's fine because Leonard dresses in Penny's lingerie as penance. We don't really have anything to say about any of this. Apparently the scene was amusing.
The episode ends with Amy requesting (after 6 months, and after telling Sheldon to his face that he was immature, selfish and emotionally and physically difficult as a boyfriend) to be his girlfriend again, at which point he wisely recognizes that he is not particularly suited to being her boyfriend, and that they were better off as friends.