|The Friendship Algorithm|
Season 2, Episode 13
January 19, 2009
"The Killer Robot Instability"
"The Financial Permeability"
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Extended PlotEditSocially awkward, Sheldon develops a scientific procedure (the titular "Friendship Algorithm") for making friends. He needs to use an open science grid computer that is in Kripke's office, but Leonard tells Sheldon that only Kripke's friends can use it. After repeated rebuffs from Kripke, Sheldon goes to a bookstore to research making friends. He finds a children's book on the subject and tries to make friends with a little girl whom he finds that he has things in common with. After inviting her to the zoo, he is hurried out by Leonard who notes that he is in direct view of a security camera and might be picked up for pedophilia. Sheldon then designs a flowchart for making friends. Sheldon follows his algorithm and gets stuck in a loop asking Kripke hobby after hobby. Howard helps him out adding a loop and counter making him choose the least objectionable hobby. He goes rock climbing with Kripke, but faints halfway up when he sees how far he has come. Sheldon invites him over to his apartment, much to the disgust of everyone else. Raj is informed he is being replaced by Kripke as five friends would be too many to handle. Kripke then tells Sheldon that there is a sign-up sheet for the computer and he has no control over it. Sheldon then dismisses Kripke as his friend and goes back to his other four friends: Leonard, Howard, Raj, and Penny.
Penny: What about Howard and Raj, how did Sheldon become friends with them?
Leonard: I don't know...how do carbon atoms form a benzene ring? Proximity and valence electrons.
Penny: Well, yeah, sure, when you put it that way.
Sheldon (on phone): Hello. This is Sheldon Cooper. I’m leaving a message for Barry Kripke. Barry, it was pleasant seeing you today in the cafeteria. I saw that you purchased the chef’s salad. Apparently, you did not know that the chef’s salad is kitchen trickery, to utilize scrap meat. Nevertheless, I hope you enjoyed it. I’m following up on our pending friendship, and I look forward to hearing from you regarding its status. Sheldon Cooper.
Sheldon (picks up train): Oh my! That’s awfully sticky. Alright, let’s see. Bernie Bunny has Two Daddies Now. It’s probably about homosexual rabbits. Jerry the Gerbil and the Bullies on the Bus. Read it, not helpful. Oh! Here we go. Stu the Cockatoo is New at the Zoo. Author Sarah Carpenter lives in Fort Wayne, Indiana, with her husband and best friend Mark, and their cockatoos too. Hardly makes her an expert in making friends, wouldn't you agree?
Little girl: I don’t like birds, they scare me.
Sheldon: Me too! Most people don’t see it. What are you reading?
Girl: Curious George.
Sheldon: Oh, I do like monkeys!
Girl: Curious George is a monkey.
Sheldon: Somewhat anthropomorphized, but yes. Say, maybe sometime you and I can go see monkeys together. Would you like that?
Leonard: Sheldon, what are you doing?
Sheldon: I’m making friends with this little girl. What’s your name?
Sheldon: Hi, Rebecca, I’m your new friend, Sheldon.
Leonard: No, you’re not, let’s go.
Sheldon: We were really hitting it off.
Leonard: Don’t look up, there’s cameras.
- "Those writers love Sheldon. He is the reason this show is on the map in many ways. At present he is also the reason it will never become more than it." - The TV Critic's Review
- IMDb user reviews
- Title Reference: The algorithm created by Sheldon that he uses to make friends.
- Chuck Lorre's vanity card 
- This episode was watched by 11.10 million people with a rating of 4.0 (adults 18-49).
- When Leonard drags Sheldon out of the bookstore, he still has a copy of "Stu The Cockatoo Is New To The Zoo" in his hand. It is unknown whether he went back and paid for it or not.
- Sheldon innocently tries to make a friend; however, Leonard takes him out of the store before someone thinks he's stalking little children. Sheldon was also stopped doing something similar to pedophiliac action by Leonard in "The Contractual Obligation Implementation", another episode where he talks to a young girl.
- The "big-balled raccoon" Howard drew on his Sheldon trivia sheet is a Bake-Danuki.
- The aspect that Sheldon likes monkeys (and also trains) is strongly regarded in this episode as does his future girlfriend Amy.
- When Kripke hits on Penny, Howard says to her "Suddenly I'm looking pretty good, huh?", referencing the previous episode, where Penny comments on Howard's interest in her.