The Guitarist Amplification

The Guitarist Amplification is the seventh episode of the shows third season.

Summary
An argument between Leonard and Penny proves "inconvenient" to Sheldon. We learn that Sheldon's parents argued a lot when he was growing up, and he doesn't like to hear people arguing at all. Penny had invited a former lover (male guitarist) to stay at her place without talking to Leonard beforehand, which Leonard was quite upset about. Everyone else was arguing, too: Raj and Howard, Raj and his parents, and Howard and his mother. Sheldon even went to the Cheesecake Factory; by himself to try to talk Penny into apologizing to Leonard so he could get on with his life. At the end of the show, Penny's friend is seen sleeping on Sheldon's couch as Leonard and Penny are in bed together in her apartment.

Title reference: Penny's friend's occupation as a guitarist.

Quotes

 * (The Guys are in the comic book store while Howard and Raj are starting to argue to Leonard about who was to blame in Leonard's and Penny's argument about Justin.)
 * Raj (To Leonard): It's like my friend Beyonce says: "If you like it, then you should've put a ring on it."
 * (Leonard looks confused)
 * Howard: Oh, come on, at the very least when she found out Leonard was upset about it, she should have backed off.
 * Raj: You mean like when a guy is upset because his friend agreed to go to cooking class with him and then doesn't show up because he was doing a juicefast with his mother?
 * Howard: I didn't know you were upset about that.
 * Raj: Really? Did miss all the subtle indicators like me saying "Howard, I am upset"?!
 * (Sheldon notices them fighting.)
 * Howard: OK, I'm sorry
 * Raj: Maybe it must mean something different in this country, but back in India, it means you are upset with a guy named Howard!
 * Howard: I said, "I'm sorry"
 * Raj: Sorry doesn't make it up to the fact that I had to make Chicken and Rice with this vegan guy. Do you know what vegan chicken and rice is? RICE!
 * Howard: Yeah, well did you think I was having fun sitting up all night listening to my mother saying to me, (in his mother's voice) "have you ever peed so much in your life?"!
 * (Sheldon is getting upset and stressed by Howard and Raj's fight.)
 * Raj: Oh my God! You are such a Mama's boy!
 * Howard: Hey! Don't bring my mother into this!
 * Raj: You brought your mother into this!
 * (Sheldon finally loses his temper at them.)
 * Sheldon: STOP IT, both of you! All this fighting, I might as well be back with my parents
 * (imitating mother) Damn it George; I told you if you didn't quit drinking, I'd leave you!
 * (imitating father) Well I guess that makes you a liar, 'cause I'm drunk as hell and you're still here!
 * (imitating mother) Stop yelling! You're making Sheldon cry.
 * (imitating father) I'll tell you what's making Sheldon cry is that I let you name him Sheldon!
 * (Sheldon storms out of the store and everyone is dazzled.)
 * Howard: Well what got him so upset?
 * Raj: Oh sure, you can tell when Sheldon is upset.