The Platonic Permutation - S9-E9
Continuity mistake: In episode 16 of season 1, Penny is talking about making a cake for Leonard's birthday and states she knows his birthday because she was checking a horoscope for him. But in this episode she does not know when his birthday is, which leads to Leonard revealing he was secretly reading Penny's diary. (00:40:00)
Suggested correction: It's certainly possible to forget something you knew eight years ago.
This is perhaps true for two people who rarely have contact, but I would list this as a character mistake. Penny and Leonard are in a serious relationship and are married at this point.
This is also a couple who BOTH forgot it was their anniversary.
I forgot my wife's birthday on a number of occasions. It's one of the reasons she is now my ex-wife.
There's a difference between forgetting and not knowing.
The Relaxation Integration - S11-E3
Character mistake: When Sheldon is telling Leonard, Amy and Penny about how his voice is like a white James Earl Jones, he quotes the famous Darth Vader line "Luke, I am your father." This is an example of the Mandela Effect, that apparently even Sheldon Cooper is susceptible to. Darth Vader actually says "No. I am your father."
The Russian Rocket Reaction - S5-E5
Character mistake: Sheldon says he drove for hours in a bus to meet Wil Wheaton. He meant he rode on a bus. Sheldon never would've made that semantic error.
The Retraction Reaction - S11-E2
Continuity mistake: Sheldon's formulae are written on three whiteboards. The marker color on the leftmost board is first red, later black. (00:07:05 - 00:09:21)
The Proton Regeneration - S11-E6
Character mistake: While bedridden after his vasectomy, Howard asks Bernadette to grill up a couple steaks instead of picking up Chinese for dinner. She gives him a disapproving look and he says "Kung Pao Chicken, please." A major ingredient of Kung Pao Chicken is peanuts. A major allergy for Howard is peanuts. (00:09:04)
Suggested correction: Since they are both quite well aware of it, they likely have either found a Chinese restaurant that doesn't use them, or they get it without peanuts.
Yup. My friend is allergic to peanuts and our local Chinese restaurant makes hers with almond instead of peanut.
Character mistake: Raj cannot talk with a woman around, but when Leonard claims they'd have to cut him in half to play teams, he blatantly argues back, and Penny is present with them. Regardless of if he was facing her or not, he shouldn't have said anything.
The Ornithophobia Diffusion - S5-E9
Factual error: Sheldon is fearful of the bird on his windowsill, which he identifies as a blue jay. Blue Jays are not native to CA. The bird is actually a scrub jay. Sheldon would know this because of his lifetime fear of birds.
The Adhesive Duck Deficiency - S3-E8
Factual error: Maybe I'm wrong but I've had the dislocated shoulder experience and shouldn't hers be in a sling at her side not across her front right to left? This just seems odd.
Suggested correction: That type of sling is the best for preventing movement of the shoulder joint. It is the proper one.
Factual error: Characters sometimes talk to one another on video calls, and a character (A) often watches these from an angle rather than face on, allowing the viewer to see both character A and the character on the call (B). When this happens, character B is shown turned a little to one side, to give the impression that they are looking directly at character A (as they would be if they were present in the same room). In reality, this means that character B is looking off to one side of their monitor and not at the image of character A, something that it makes no sense to do. No matter what angle the laptop is shown from, provided character B is visible, they should appear to be facing the viewer.
Suggested correction: Since we almost always see these video calls using full-screen, people sitting side-by-side would be on different sides of the screen. You wouldn't look into the webcam itself to see them. You would look at the screen, and move your head slightly to look at the left part versus the right.
The Clean Room Infiltration - S8-E11
Other mistake: When Howard, Leonard, and Raj are arguing in the clean room, Howard says that Leonard is jealous because Howard and Leonard used to be "best friends until Koothrapali came along." Yet, in the earlier seasons, we know that Howard and Raj already knew each other when Leonard met them for the first time and brought them back to the apartment to play video games. Meaning they couldn't have been best friends before Raj came along.
The Werewolf Transformation - S5-E18
Character mistake: In S5-15, Sheldon is asking his friends to take him to SuperCuts. But in this episode, he goes to Mr. D'Onofrio's barber shop where he says he's gone to since he moved to CA, and he said D'Onofrio had his "haircut records."
The Hamburger Postulate - S1-E5
Continuity mistake: Leonard and Leslie are rehearsing the violin and cello in the guys' living room, and when they leave the room to go to Leonard's room, Leonard's cello and stand are still in front of the comfy chair. When Sheldon gets home, the cello and stand are gone, and only Leslie's closed violin case is left on the sofa. And she picks it up and leaves with it. How did the violin get back in the case.
The Retraction Reaction - S11-E2
Deliberate mistake: Leonard is on NPR on a Friday, and the guys don't talk about it until the following Monday at work. They spend so much time together, they surely would've discussed it sooner.
The Retraction Reaction - S11-E2
Character mistake: When Leonard arrives at the Human Resources office, he tells the HR person that he's not used to being called into the Dean's office. He's not in the Dean's office, he's in HR.
The Convergence Convergence - S9-E24
Other mistake: Howard believes he's being followed by the government, when it's actually Leonard, Penny, and Beverly in their car. The shots from Howard's car show only Leonard's silhouette. The other two do not appear as silhouettes.
The Higgs Boson Observation - S6-E3
Factual error: Sheldon tells Alex that he's run a background check, including her medical records. There is no way he could obtain medical records without a HIPAA authorization signed by Alex herself. It's illegal.
The Countdown Reflection - S5-E24
Continuity mistake: Penny mentions that she knows lots of people who got married in Las Vegas. In episode 7/9, she discovers that her "fake" wedding to Zach in Vegas was real.
Continuity mistake: Sheldon puts the bag of takeout into the lobby trash can and as he does so, the whole bag turns sideways. At the end of the scene, he takes the bag out of the can and it's upright without him turning it.
Continuity mistake: When Leonard is consoling Penny on the couch, the blue Afghan she has with her constantly changes position, including jumping from the floor back to the couch.
Continuity mistake: Throughout the early episodes, shots of Sheldon's bathroom shows the door open and a rack of towels against the wall. Later episodes show that that area is actually where the sink and mirror are.
