Revealing mistake: In the scene where Leonard is supposedly playing Halo 3 against somebody in Copenhagen, there is no ethernet cable or wireless adapter connected to the Xbox 360 (one of the originals without wireless inbuilt), which means that there is no way he can be playing online with someone in another country. (00:09:00)
Continuity mistake: When Penny asks Sheldon "What trauma?" in the electronics store, Sheldon holds two boxes - one with an orange side on top of one with a black side. In the next shot the black sided box is on top of the orange one. The boxes then continue to swap places during the whole scene. (00:11:50)
Continuity mistake: In the electronics store, when the man asks Sheldon which hard drive he should buy in the first shot he is holding the green box in his left hand. Next shot it is under his arm. (00:12:50)
Continuity mistake: Penny throws a black iPod out the window, but when Raj comes in having found it on the ground outside he has a silver one. (00:01:00 - 00:02:45)
Continuity mistake: When Penny is squirting chocolate syrup in the ice cream container, she drizzles some on the lip of the carton, causing it to run down the outside. The camera switches to Leonard and then back to Penny, at which point, the chocolate is gone. (00:04:50)
Continuity mistake: When Penny is talking to Leonard about who read her Ex's blog, she has a spoon full of ice-cream. Camera cuts and it's now empty. (00:05:00)
Character mistake: When Leonard and Sheldon sit down for lunch at work, Sheldon grabs the salt and pepper and begins to shake the "shakers" over his food. However, these are grinders and not shakers. He would have had to twist the tops in order to get any salt or pepper. (00:16:10)
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.
Character mistake: At the very beginning of the episode Leonard says "So you see what you're eating is not technically yogurt because it doesn't have enough live active acidophilus cultures." He is implying this is a scientific fact (he's not just giving his opinion on yogurt.) But to meet the U.S. standards for yogurt, only the starter cultures Lactobacillus bulgaricus and Streptococcus thermophilus are required, not Lactobacillus acidophilus. The presence or absence of L. acidophilus does NOT determine a food's identity as yogurt (which Leonard's line is implying). (00:00:05)
Continuity mistake: Right at the start of the episode, Leonard kisses Penny. When he starts kissing her his head is tilted to the right (opposite side to the wall with the camera). When they move to the camera image, his head is tilted to the left (on the side with the camera), and when they move back his head is back tilting to the right again. (00:00:30)
Continuity mistake: When Sheldon is undoing a pair of socks that Penny has paired, Penny is seen holding a single sock. Camera changes and she now has nothing in her hands. This is an instant cut. No time to drop it. (00:05:50)
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)
Continuity mistake: When Sheldon is sitting with Raj in his apartment watching television, the can of soda on the table in front of him rotates itself a couple of times. (00:14:40)
Factual error: Raj and Sheldon are watching TV in Raj's apartment and we hear music playing. Sheldon asks if the woman on TV was Aishwarya Rai to which Raj says yes and then they argue about her and Madhuri Dixit. The song playing was from the Bollywood movie Kaho Na Pyar Hai, but neither of them are in the movie - the lead actress was Ameesha Patel. (00:14:50)
Continuity mistake: When Leonard says he is happy Penny is moving on he has nothing in his hand. Camera cuts and now he is holding a bit of bread. (00:03:00)
Continuity mistake: When Leslie and Leonard are talking about starting a relationship again, the can of Diet Cola keeps rotating. In some shots from Leslie's point of view you can't see the logo and in others you can. (00:06:30)
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: When Sheldon and Penny are talking at the end on the stairs, Penny's hands keep changing from clenched to hanging down.
The Barbarian Sublimation - S2-E3
Continuity mistake: At the start, after Penny has dropped one bag, there is an item in the top of the remaining bag. This item keeps appearing and disappearing. (00:01:20)
The Barbarian Sublimation - S2-E3
Continuity mistake: After Penny drops her bags of groceries whilst trying to unlock her door, the dropped items change their positions between shots (note the items against the wall.) (00:02:05)
Answer: Because Raj's selective mutism seems to be caused by women that Raj sees (on some sort of conscious or subconscious level) as a potential sexual partner. An attribute that wouldn't apply to either his sister or mother.