In the show, the song "Soft Kitty" was described by Sheldon as a song sung by his mother when he was ill. Its repeated use in the series popularized the song. A scene depicting the origin of the song in Sheldon's childhood is depicted in an episode of Young Sheldon, which aired on February 1, 2018. It shows Sheldon's mother Mary singing the song to her son, who is suffering with the flu.
The men are excited that Bill Gates is visiting Penny's pharmaceutical company, although she says that she cannot bring them along. Sheldon believes that it's an April Fools' Day prank. Leonard sees what hotel Gates is staying at on Penny's schedule, so he, Raj and Howard meet him in the lobby the day before. Once Sheldon sees proof, the men twice send him to the wrong hotel as real pranks. Penny says Leonard can meet Gates for real, so he fakes being sick to avoid him. When Penny puts Gates on a video call, he recognizes Leonard from the previous night. Meanwhile, Amy is tired of Bernadette only talking about her children, so Bernadette uses her expanded parental brain to learn random science facts.
Initial reception for the series was mixed. The review aggregation website Rotten Tomatoes reported a 52% approval rating for the first season based on reviews from 23 critics, with an average rating of 5.18/10. The website's critical consensus reads, "The Big Bang Theory brings a new class of character to mainstream television, but much of the comedy feels formulaic and stiff." On Metacritic, the season holds a score of 57 out of 100, based on reviews from 23 critics, indicating "mixed or average reviews". Later seasons received more acclaim and in 2013, TV Guide ranked the series #52 on its list of the 60 Best Series of All Time.
However, no legal action was required to end production of the other show: as soon as it became known that the show was unlicensed, the actors quit and the producers canceled it. Dmitriy Tankovich (who plays Leonard's counterpart, "Seva") said in an interview, "I'm upset. At first, the actors were told all legal issues were resolved. We didn't know it wasn't the case, so when the creators of The Big Bang Theory started talking about the show, I was embarrassed. I can't understand why our people first do, and then think. I consider this to be the rock bottom of my career. And I don't want to take part in a stolen show".
In scenes set at Howard's home, he interacts with his rarely-seen mother (voiced by Carol Ann Susi until her death) by shouting from room to room in the house. She similarly interacts with other characters in this manner. She reflects the Jewish mother stereotype in some ways, such as being overly controlling of Howard's adult life and sometimes trying to make him feel guilty about causing her trouble. She is dependent on Howard, as she requires him to help her with her wig and makeup in the morning. Howard, in turn, is attached to his mother to the point where she still cuts his meat for him, takes him to the dentist, does his laundry and "grounds" him when he returns home after briefly moving out. Until Howard's marriage to Bernadette in the fifth-season finale, Howard's former living situation led Leonard's psychiatrist mother to speculate that he may suffer from some type of pathology, and Sheldon to refer to their relationship as Oedipal. In season 8, Howard's mother dies in her sleep while in Florida, which devastates Howard and Stuart, who briefly lived with Mrs. Wolowitz.
The scene is all business – at least as much as you can expect from a bunch of cut-ups making a sitcom – and no one seems distracted by two significant events: The episode will mark the show’s 276th, moving it past “Cheers” to set a record for a sitcom filmed in front of a studio audience, and only three more remain to be shot for "Big Bang," co-created by Chuck Lorre and Bill Prady.
Sheldon needs half a billion dollars to prove his latest concept of string theory, which the University cannot afford to fund. Crowdfunding and selling some of his most valuable comic books to Stuart give him a small start. When Raj mentions gambling in Las Vegas, Sheldon goes there but is caught calculating odds by security before he can make any bets. Meanwhile, Amy takes Penny and Bernadette shopping for her wedding dress. She loves an old-fashioned one that the other girls admit that they find ugly, though Penny assures Amy she can make her own decisions about her wedding. Sheldon, however, comes home and sees Amy in the dress and loves how she looks.