The Hamburger Postulate

"The Hamburger Postulate" is the fifth episode of the first season of the  sitcom The Big Bang Theory. This episode first aired on October 22, 2007.

Summary
Leslie Winkle seduces Leonard, but only wants a one night stand. Leonard is fixated on what Penny thinks of it all.

Extended Plot
The show opens with Leonard and Sheldon beating Raj and Howard when they recreated the (with major alteration). Penny comes to take their order, when they bump into Leslie Winkle. She tells Leonard that the Physics Department Orchestra needed a cellist, Leonard agrees seeing as he plays the cello. Penny asks whether there was anything going on between Leslie and Leonard. Leonard tried to deny it, but Sheldon abruptly said "He asked her out once, it was an embarrassing failure". Penny mentioned they would have made a cute couple. When the Physics Department Orchestra was rehearsing Leslie hinted sexually towards Leonard by saying "I admire your fingering, maybe next time you can try that on my instrument" and after that when, Leonard and Leslie were practicing alone, she said she was sexually available. After a brief conversation about Penny and "musical foreplay" Leonard and Leslie rushed to his room and initiated sexual intercourse. A distressed Sheldon calls Penny to his apartment to interpret a " on the doorknob", Penny explains to him that the tie meant the people in the room didn't want to be disturbed because they are "getting busy", Sheldon told Penny that other than Leonard, Leslie was probably behind the door, Penny says "Good for them" in a doubtful tone. The following morning, Sheldon wakes up to a terrible surprise; the equations on his white board had been tampered. Although it solved the problem he had, he was still infuriated. Shortly after that, Leslie admits that she had corrected his equations. Later, Leonard bumps into Penny who asked him how was it (sexual intercourse) last night, which made Leonard ponder on whether he wanted Penny or Leslie, though he settled for Leslie as she is currently making him happy. Then, he tried to make his moments with Leslie more intimate, but Leslie revealed that the sexual intercourse had no emotional ties, leaving Leonard a little heartbroken. At the final scene, Sheldon explains his interest for the Cheesecake Factory's hamburger (Title Reference), Penny comes along and asks how Leonard is doing with Leslie, after he explains the situation Penny says "...I'm sure there is someone out there who is just right for you" and walks away from them with a hidden smile. Leonard ponders if what Penny said "means anything".

Quotes

 * Penny: Leonard, I didn't know you played the cello.
 * Leonard: Yeah, my parents felt that naming me Leonard and putting me in advanced placement classes wasn't getting me beaten up enough.

Trivia

 * Sheldon says, ". The study of signs and symbols, it’s a branch of philosophy related to ." Interestingly, Sheldon's favorite character whom he tries to emulate, Spock, led his year in Semiotics, among other disciplines, at, according to Marvel-Paramount Comics Star Trek Early Voyages #1: Flesh of My Flesh.
 * Leonard Hofstadter states, " are magic, Superman is vulnerable to magic..." &mdash; Superman's powers are derived from the yellow sun of Earth; they have no magical component, leaving the " Man of Steel" open to malignant sorcery (Superman: The Ultimate Guide to the Man of Steel, Superman vs. Magic). On the other hand, Superman similarly battles an ogre in Justice League of America Vol. 1 #49 (November 1966) with no ill effect.
 * Leslie points out that she saw Leonard's pupils dilate, which "unless [he's] a heroin addict, points to sexual attraction". Heroin however is an opiate, and opiates cause pupils to constrict, not dilate. Stimulants however (cocaine, caffiene etc.) do cause pupils to dilate. To put it simply, Leslie's terminology is incorrect.

Critics
"A very enjoyable episode of comedy and character development. It’s always difficult to put a new spin on sex jokes because we have seen a million of them. But Leslie’s dead pan science seduction is funny and Leonard’s character comes out looking sweet. Good job." - The TV Critic's Review