While playing SWTOR, Leonard tells Raj the Empire is on his tail, indicating they are playing Republic characters, which is further supported by the view of Raj's laptop. However, the screen shot of Bernadette's character clearly shows she is playing a Sith Inquisitor (armor in SWTOR is specific to both class and faction).
Sheldon is heard saying 'Legos' even though 'Legos' is wrong. According to The Lego Group itself, the proper usage is 'Lego bricks', 'Lego pieces', 'Lego sets', etc. Never 'Legos'.
Stuart offers Excalibur to Sheldon as a gift for Amy's aunt, to use as a cane. In The Russian Rocket Reaction (2011), Sheldon and Leonard considered buying Longclaw (Jon Snow's sword from Game of Thrones (2011)), but
Sheldon wasn't sure if it was the right sword to start their sword collection. Leonard asked what sword he wants and Sheldon says Excalibur. Leonard said Stuart didn't have Excalibur. EDIT: Since Sheldon wanted Excalibur, it's easy to believe that he got it from somewhere else.
As Raj is walking up the stairs with Leonard and Howard, he suggests 48 hours of online Star Wars gaming, starting Saturday morning. 48 hours from Saturday morning would be Monday morning, meaning the guys would all be leaving for work from Sheldon and Leonard's apartment.
While playing the drinking game with Amy, Penny says, "Now I will drink this entire cup of beer", but all three cups are only half full.
Sheldon says he is going to run around outside with a wet head and try to catch a cold. He should know that a wet head has nothing to do with catching colds.