The Cohabitation Formulation - S4-E16
Character mistake: When Penny says she smells Chinese food and Sheldon corrects her by telling her she's slipping because it's Thai, Sheldon is eating the food with chopsticks, even though in a previous episode he uses a fork and spoon because that's how Thai people eat their food. (00:19:15)
The Vengeance Formulation - S3-E9
Factual error: Sheldon's voice becomes squeaky when helium is pumped into his office. But if the room contained enough helium to make his voice squeaky just by breathing, Sheldon would actually be suffocating due to lack of oxygen, the lighter helium having displaced the heavier oxygen. You can do it with a balloon because you can breathe normal air between huffs, but if you're in a room full of helium, you won't last long before passing out and asphyxiating.
The Excelsior Acquisition - S3-E16
Character mistake: When Howard finds the stack of paychecks in Sheldon's drawer and wonders why Sheldon hasn't cashed them, Sheldon explains that he's saving them to purchase items that have yet to be invented and he doesn't trust banks. But just keeping them in his drawer doesn't do anything, because checks are voided after a set period of time and they would eventually become worthless.
The Convention Conundrum - S7-E14
Character mistake: On Sheldon's board of possible attendees for his convention he has misspelled Ian McKellen - with 'an' at the end.
The Vengeance Formulation - S3-E9
Factual error: In order to get vengeance on Kripke, Sheldon mixes a solution of hydrogen peroxide, saturated potassium iodide and liquid soap, creating a large foam blob. This is easy to replicate, and what you will get (and look carefully, it is what Sheldon gets) is a huge, aerated foam mass consisting almost completely of bubbles. It is barely heavier than air, and if dropped from a ceiling as we see later in the episode it would float harmlessly about the place. Whatever it is that drops on Kripke and his visitors later, it isn't the foam mixture we see earlier - it looks like some sort of custard mix.
Other mistake: Leonard says he had a growth spurt after his high school prom. In "The Cooper-Hofstadter Polarization" he told Penny that he still had all his clothes he owned since the eighth grade, after his last growth spurt.
The Discovery Dissipation - S7-E10
Continuity mistake: The Stevenson Award in Sheldon's office reads "Sheldon Cooper, PhD." But, in the "Dennis Kim" episode we are told Sheldon was 14.5 years old when he earned that award - 1.5 years before earning his PhD at age 16, so the award should not show the title of PhD.
The Skank Reflex Analysis - S5-E1
Continuity mistake: At the start of the episode, Raj's Sirkist can rotates itself on the table.
The Fuzzy Boots Corollary - S1-E3
Continuity mistake: When Sheldon is telling Leonard that he didn't ask Penny out, there is a yellow food-bag on the counter between them that keeps changing its position with every shot change. (00:11:15)
The Hamburger Postulate - S1-E5
Continuity mistake: At the end when Sheldon has got a burger, the amount of burger left changes depending on the camera angle. Most noticeable when he asks Penny about permanently reserving the table - between shots the lettuce disappears, the bun changes colour, and the bite marks change.
The Hawking Excitation - S5-E21
Character mistake: The sign on Howard's laboratory door reads "RESTICTED area".
The Hamburger Postulate - S1-E5
Character mistake: Leslie states that heroin causes pupils to dilate, like when Leonard sees Penny. Opiates cause pupils to constrict. (00:06:20)
The Boyfriend Complexity - S4-E9
Continuity mistake: In 2-15 "The Maternal Capacitance" Penny explains to Beverly, referring to her father, "My mom could have just said 'Bob, get over it, she's a girl'". But in this episode Penny's father is named Wyatt.
Factual error: The main apartment in the show is located in Pasadena, Calif. When looking out the window in the background, mountains are shown in the distance and far away. In reality, Pasadena lies right underneath the long mountain range so the mountains would be up close, not far away.
Suggested correction: Not true. I lived in Pasadena for years and in some areas, the mountains do look further away. The view from the San Pasqual apartments, you can barely see the mountains.
The Junior Professor Solution - S8-E2
Character mistake: When Howard is asking Sheldon engineering questions, the first question is "How do you quantify the strength of materials?" Sheldon answers "Young's Modulus," and Howard admits that is correct. But it's not correct - Young's Modulus quantifies a material's elasticity, not strength. (00:17:10)
Character mistake: When Sheldon arrives at the apartment with his Nintendo 64 in the box, he tells Leonard that they can play Super Mario 64. He then proceeds to say, upon finding a memory card, that they can pick up where he left off. Super Mario 64 does not make use of the memory card for progression, all of that data was saved on the cartridge. (00:07:25)
Continuity mistake: In the laundry room when Penny is talking to Sheldon, Sheldon takes some time arranging a blue shirt on his plastic laundry folder. Then it suddenly turns into a pair of socks, which he folds and then picks up the blue shirt again. There was not enough time for him to switch out the shirt for the socks. (00:06:30)
The Cruciferous Vegetable Amplification - S4-E2
Character mistake: In the first scene, on Sheldon's board are the words "D-D Fushion." This should be fusion. Sheldon wouldn't make a mistake like that.
The Long Distance Dissonance - S10-E24
Continuity mistake: After the 'Ramona' conversation between Sheldon and Penny ends, Sheldon leaves Penny alone on the couch. Penny looks up to the "Amy and Penny" painting and says "Don't look at me like that, I tried." In S10 E10, Amy gave the painting back to Penny, which was hung in Leonard's living room.
The Thespian Catalyst - S4-E14
Revealing mistake: When Sheldon goes to Penny's apartment and they do a scene study together, they both read lines from a multi-page script that Sheldon brings with him. On a couple of occasions the camera cuts to a side view of Sheldon and we get to see the page of the script that he's currently reading from. The pages are completely blank.
