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.
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 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 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 Retraction Reaction - S11-E2
Character mistake: When speaking on the radio, Leonard says he has never heard himself through headphones. We have seen him several time wearing headphones while speaking, for example during a podcast with Will Wheaten and on Science Friday too.
The Long Distance Dissonance - S10-E24
Continuity mistake: When Sheldon takes a plane to see Amy in Princeton, the plane he is on has 2 engines when it takes off and 4 engines when it lands. It's a direct flight from LAX so he wouldn't have changed planes.
Factual error: Every time we see Leonard's laser lab the door is open and he is able, if the story requires it, to fire the laser. As evidenced by the several safety notices visible and the scripted requirements for characters to put on safety goggles it should not be possible to activate the laser while the lab door is open - it would be interlocked, meaning the laser wouldn't function unless the door is closed.
The Beta Test Initiation - S5-E14
Character mistake: Sheldon says (during Fun With Flags) "But like the flag over Fort Sumter, I'm still here." The Sumter flag was lowered when the fort surrendered to the Confederates. The flag over Fort McHenry was never taken down despite the British bombardment and inspired Francis Scott Key to write the National Anthem about it. Whouldn't a vexologist know that?
Suggested correction: Sheldon is referring to the actual Fort Sumter flag, which still exists and is on display at the Fort Sumter museum.
Sheldon is not referring the actual flag (especially since if the actual flag is in a museum it's not still over Fort Sumter). Sheldon is referencing the line from The Star-Spangled Banner "our flag was still there." Key wrote The Star-Spangled Banner after seeing the flag over Fort McHenry was still there. The writers simply made a mistake and Sheldon the character would know which flag inspired the line. Incidentally, the actual Fort McHenry flag also still exists.
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 Hamburger Postulate - S1-E5
Character mistake: When Sheldon knocks on Penny's door to seek advice about the tie on Leonard's doorknob, he does not use his typical triple knock. (00:07:43)
First time he knocks 3 times is in Episode 2 of Season 1. First time knocking 3 times followed by saying the name is episode 10 of Season 1. The ritual of 3 knocks and 3 times saying the name and then stopping is Episode 5 of season 2.
Sheldon knocks three times because he once walked into his parents bedroom and saw his father with another woman. He's been doing the triple knock since he was a teenager.
Yet, he didn't in the show till Season 2. Funny ain't it?
Suggested correction: A one-time lapse in someone's usual behavior does not count as a "character mistake", even in the case of someone given to ritualistic behavior as Sheldon is.
Ah, but in an episode he explains he had developed this particular ritual at age 13 after walking into his parent's bedroom without knocking and seeing his father having sex with another woman. He says he started knocking 3 times since then and would never forget. So its not consistent and a mistake as this is not the only example one can name.
The Benefactor Factor - S4-E15
Continuity mistake: When Sheldon and Leonard are in the kitchen discussing Leonard's upcoming night out with Mrs. Latham, there's a plastic bottle of orange juice on the table that keeps disappearing and reappearing as the camera switches between Sheldon and Leonard.
Suggested correction: The bottle is there every time, a few times because of the camera angle it is hidden by Sheldon.
The bottle of OJ is right next to a container of Coffee Mate, both items always visible when the bottle of OJ is present. When the OJ is not present, only the Coffee Mate is there, near enough the center of the table to not possibly be blocked out by either Sheldon nor Leonard.
No it is not right next to the coffee Mate, there is some distance with a phone in between. You can sometimes see the bottle behind Sheldon when he moves.
The Rhinitis Revelation - S5-E6
Other mistake: When Mary is rubbing VapoRub on Sheldon's chest, she makes a comment that last time she saw that there was no hair, to which Sheldon replies "Yeah it filled in last year." In Season 1, Episode 11, Penny rubs VapoRub on Sheldon's chest and a very clear remark about chest hair was made. Season 1 for the show was 4 years ago.
Suggested correction: Sheldon is probably joking when he tells Mary his chest hair filled in the previous year.
He doesn't understand sarcasm, hence, doesn't know when to be sarcastic.
And nearly all instances of Bazinga are not used in a funny circumstance. Indicating poor judgement and lack of knowledge regarding jokes.
They were funny to him. And to the audience.
The Cooper/Kripke Inversion - S6-E14
Character mistake: As Leonard is leaving the Mechanical Engineering lab, the sign on the door is spelled incorrectly as 'resticted area' instead of 'restricted area'. (00:04:07)
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.
The Troll Manifestation - S8-E14
Continuity mistake: When the gang and Stephen Hawking are video chatting, the Android mascot is lying down when the camera is facing the gang, but when the camera is facing Stephen Hawking, the Android mascot is standing up.
The Parking Spot Escalation - S6-E9
Continuity mistake: In this episode Penny mentions she has a sister ("I remember my first bikini wax. My sister did it with duct tape and melted Crayolas"), but in future episodes she has only a brother.
Suggested correction: While her brother was the only one that came to the wedding she mentions her many other times and never said she only had a brother. She mentions her father dancing with her and her water breaking at her wedding. She asks her dad about Randall and Lisa. She also mentions her sister "accidentally" shot her husband. So while the brother is more prominent the sister is mentioned throughout.
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.