Sheldon, Leonard, Raj and Howard are seen playing the board-game "Talisman". They make numerous mistakes while playing, such as having too many pieces, using the wrong counters, having face down cards strewn about the board and rolling two dice to move their piece.
When dining with Leonard near the end of the episode Sheldon corrects Leonard's use of the word 'nauseous' stating that it is a common grammatical error to use nauseous when the speaker means nauseated. It's actually a semantic error (as it alters the meaning of the sentence) and is actually perfectly grammatical.
When Leonard and Sheldon are discussing Leonard's date with Penny while eating lunch, Sheldon puts salt and pepper on his food. However the the salt and pepper he is using is not the kind that shakes out, but are of the grinder variety where one must twist the top back and forth to get anything out. Shaking the containers will put nothing on one's food
While Penny is pouring chocolate syrup into her ice cream container, some spills down the side. In the next shot, there is no evidence of the spill. A few moments later, the spill is back having run down the whole side of the container.
When we first see Penny eating the ice cream, some of it is visible near the top of the carton. It dips much lower without her eating any. Also, a bag of Teddy Grahams moves around the carton on the counter with no one touching it.