The Big Bang Theory Wiki

"The Hamburger Postulate" is the fifth episode of the first season of the American sitcom The Big Bang Theory. This episode first aired on October 15, 2007.


Leslie Winkle seduces Leonard, but only wants a one-night stand. Leonard is fixated on what Penny thinks of his actions. The gang has dinner at the Cheesecake Factory restaurant for the first time.

Extended Plot[]

The guys at the cheesecake factory

The guys playing an altered version of The Battle of Gettysburg.

The Hamburger Postulate 4

What does the tie mean?

Leonard and Sheldon are beating Raj and Howard when they recreated the The Battle of Gettysburg (with major nerdy alterations). Penny comes to take their order. Howard interrupts her and the whole table ignores her pursuing instead to argue about the battle. Penny excuses herself, and when she returns states that they have to order or leave and never come back. They start to give their order when they bump into Leslie Winkle. She tells Leonard that the Physics Department Orchestra needs a cellist. Leonard agrees to join 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". After that when, Leonard and Leslie were practicing alone, she said she was sexually available. Following a brief conversation about Penny and "musical foreplay" Leonard and Leslie rush to his room and initiate sexual intercourse.

A distressed Sheldon calls Penny to his apartment to get an explanation in the matter of semiotics. Penny of course does not understand. Sheldon tries to explain and it only makes things worse. Penny says, "Sweetie, I know you think you're explaining yourself, but you're really not." He asks her to accompany him and shows her a "tie 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; this fact was confirmed moments later when they heard Leslie say (in a completely deadpan tone) "Oh, Leonard, you magnificent beast." Penny says "Good for them" in a doubtful tone. Sheldon asks Penny for advise on what to do. She indicates that she doesn't really know what to tell him since she is usually the one on the other side of the tie, and she leaves. Sheldon, not knowing what else to do, calls Leonard on his cell phone. He says he saw the tie on the doorknob and his message was received and to give his best to Leslie.

The following morning, Sheldon wakes up to a terrible surprise; the equations on his whiteboard had been tampered with. 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 his sexual intercourse last night, which made Leonard ponder whether he wanted Penny or Leslie, though he settled for Leslie as she is currently making him happy.

Later that day, Leonard visited Leslie in her lab. 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. As Leonard leaves Leslie's lab, Howard confronts him about his sexual encounter with Leslie. Howard said a little bird told him.

Finally Sheldon explains his interest for the The Cheesecake Factory's hamburger, and suggests that he was going to eat there every Tuesday for the foreseeable future. Penny of course was not thrilled. Sheldon inquired who he should talk to if he wanted to reserve this table every Tuesday. Penny suggested a psychiatrist. Penny 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 wonders if what Penny said "means anything".



  • "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
  • IMDb user reviews.


  • Title Reference: Sheldon inquires about the Cheesecake Factory's hamburger meat.
  • This episode was watched by 8.81 million people with a rating of 3.5 (adults 18–49).
  • Episode transcript.

Costume Notes[]


Action Duo




Sheldon wears three t-shirts this episode. The first is the Batman Action Duo shirt, featuring Robin. While Leonard and Leslie are getting busy, he's wearing another  Goodnight celestial graphic shirt. For the final scene at the Cheesecake Factory, he's wearing the rare Captain QO t-shirt.

S01e05 blackstar

Unknown: black star

S01e05 bluegraphic

Unknown: blue graphic

S01e05 caffiene


S01e05 redshard

Unknown: red shard

Leonard wears a green t-shirt with a black star edged in red, a black t-shirt featuring the caffeine molecule, a blue shirt with an angular design, and a red shirt with a shard graphic. 


Superman buckle


Red and black Vans


Howard wears a green backed alien head pin, his uperman belt buckle, and still his red and black Vans. Playing Jinga and dancing to Latin music, he can be seen with a Coke bottle belt buckle. 


  • First time Penny serves them at The Cheesecake Factory. First time the restaurant appears.
  • Sheldon says, "Semiotics. The study of signs and symbols, it’s a branch of philosophy related to linguistics." Interestingly, Sheldon's favorite character whom he tries to emulate, Spock, led his year in Semiotics, among other disciplines, at Starfleet Academy, according to Marvel-Paramount Comics Star Trek Early Voyages #1: Flesh of My Flesh.
  • Sheldon's former favorite burger was the one from Big Boy. From his point of view the Cheesecake Factory Barbecue Burger surpasses the Big Boy because of its "much more satisfying meat to bun to condiment ratio". He even wants to declare it as the new Tuesday hamburger and tries to permanently reserve the table for every Tuesday night.
  • Leonard Hofstadter states, Orcs are magic, Superman is vulnerable to magic...", 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 (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 Winkle 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, caffeine etc.) do cause pupils to dilate. To put it simply, Leslie's terminology is incorrect.
  • Johnny Galecki (Leonard) knows how to play the cello in real life.
  • Sheldon went to college at the age of 11, which is also mentioned in the previous episode (S1E4).
  • Sheldon's Knock did not occur when he when to Penny's door.


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.
Howard: If you're into music, I happen to be a human beatbox.
Penny: Really?
Howard: (Beatboxing)
Penny: I'm actually not that into music.

Penny: (To Sheldon) Sweetie, I know you think you're explaining yourself, but you're really not.

Sheldon: I like the hamburgers where we usually have hamburgers; you can’t make the assumption that I’ll like the hamburgers here.
Leonard: I’m sorry. Give him a hamburger.
Penny: Uh, which one, the Classic Burger, the Ranch House Burger, the Barbecue Burger or the Kobe Burger?
Sheldon: Can’t we just go to Big Boy? They only have one burger. The Big Boy.
Penny: The Barbecue Burger is like the Big Boy.
Sheldon: Excuse me, in a world that already includes the Big Boy, why would I settle for something like a Big Boy?
Penny: Because you are not at Big Boy!
Sheldon: Fine, I’ll have the Barbecue Burger.

Penny: Gee, Sheldon, you’re asking the wrong girl. I’m usually on the other side of the tie.

Sheldon: Hold on, h-hold on! (clearly peeved)
Leslie: What?
Sheldon: Who told you, you could touch my board?!
Leslie: No-one.
Sheldon: I don't go into your house and touch your board!
Leslie: There are no incorrect equations on my board. (Leonard grins, Sheldon is furious)
Sheldon: Oh, that is so... so...
Leslie: I'm sorry, I gotta run. If you come up with an adjective, text me. (exits)
Sheldon: Inconsiderate. That is the adjective. Inconsiderate. (Pulls out his phone to text her.)

Sheldon: You're a lucky man Leonard.
Leonard: How so?
Sheldon: You're talking one of the three men in the western hemisphere who can follow your train of thought.
Leonard: So what do you think?
Sheldon: I said I could follow it. I didn't say I cared.

Sheldon: My equations! Someone's tampered with my equations!
Leonard: Are you sure?
Sheldon: Of course I'm sure! Look at the beta function of quantum chromodynamics! The sign's been changed!
Leonard: Oh, yeah...but doesn't that fix the problem you've been having?
Sheldon: Are you insane? Are you of your mind? Are you- hey, look, that fixed the problem I've been having!
Leslie: (enters) You're welcome.
Sheldon: You did this?
Leslie: Yeah. I noticed it after I got up to get a glass of water, so I fixed it so now you can show that quarks are asymptotically free in high energies. Pretty cool, huh?
Sheldon: Cool?!

Sheldon: Who do I talk to about reserving this table every Thursday?
Penny: I don't know. A Psychiatrist?