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.
The Wheaton Recurrence - S3-E19
Factual error: Sheldon and the team are league bowling and have a match with Will Wheaton's team. They are bowling on lanes 2 and 3. In league bowling, you have to bowl on lanes that start with an odd number because the ball return is shared between those lanes. In league bowling, you take turns with each lane so that any differences in the lanes evens out, and this lane layout wouldn't allow that.
Continuity mistake: In the early episodes, Leonard is depressed and buys cat stuff. He comments that he has taken in to account Sheldon's asthma with a hyper allergenic cat. Later in the series it is Leonard with asthma and Sheldon who gets all the cats.
Suggested correction: Presumably Sheldon also buys non-allergenic cats.
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.
Continuity mistake: In the beginning of the series Sheldon knocks on Penny's door only once. Later in the series Sheldon explains he has always knocked 3 times because he walked in on his father with another woman.
Deliberate mistake: Whenever anyone walks across the front hallway, it takes them 6-7 seconds to walk from one stairway to the other. On the backside of the stairway, it only takes 1-2 seconds to walk across.
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.
The Colonization Application - S8-E17
Character mistake: Leonard and Penny were using the body paint the second time, the entire canvas is covered, and they each are covered with paint. But not a bit got into their hair.
The Hamburger Postulate - S1-E5
Continuity mistake: When Sheldon is explaining to Leonard why a Cheesecake Factory Hamburger is superior to a Big Boy Hamburger the number of fries on Leonard's plate noticeably changes between shots.
The Bow Tie Asymmetry - S11-E24
Continuity mistake: After the ceremony, as Amy and Sheldon are walking down the aisle, different camera angles show Barry Kripke holding the microphone in different hands but without changing them as he is singing.