While Sheldon and Penny are down in the laundry room, they are talking and folding Sheldon's laundry. Sheldon is using his folding device. After Sheldon asks Penny if she knows Klingon, or any card tricks, he reaches for and inserts a blue t-shirt into the folding device. Penny admits that she lied to Leonard about finishing Community College. Sheldon then uses the folding device but removes a colorful pair of socks, not the blue t-shirt.
The address for Howard's house has changed. In The Dumpling Paradox (2007), the address was 3150, as seen to the left of the door, below the porch light. Now, and for the rest of the show, the address is 845, as seen to the right of the door. Given that Howard "sleeps in the same room where his bassinet was" (as stated by Leonard in The Maternal Capacitance (2009)), it is obvious that the Wolowitz's could not have moved.
When Leonard and Sheldon come home from work carrying their bags, as they're arguing while they walk in the door, Leonard's right hand is twitching slightly. It then cuts to a closer shot of him and his hand is still.
When Sheldon comes over to stay at Rajesh's place, Rajesh is watching a Hindi movie and a song is audible for a few seconds. Sheldon asks Rajesh if that actress is Aishwarya Rai Bachchan and Rajesh says she is. But the song is from the movie Kaho Naa... Pyaar Hai (2000) which does not star Aishwarya Rai at all. At the start of the scene there is one more piece of music that is heard - a classical Indian tune. The music is never played in the movie, or at least, it is not played any time near the two occurrences of the song.
After Sheldon tells Penny he is not capable of keeping secrets, she tells him to "just forget about it". To this, Sheldon replies: "Forget? This mind does not forget" and explains how he has not forgotten anything since his mother stopped breastfeeding him. However, later in the episode he forgets aboutLee Meriwether being one of the actresses who played Catwoman and about Professor X and Nightcrawler being two of the X-men.