
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)
Continuity mistake: When Sheldon and Penny are talking at the end on the stairs, Penny's hands keep changing from clenched to hanging down.






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.