Sheldon at first declines coffee telling Penny "Coffee's out of the question. When I moved to California, I promised my mother I'd stay away from drugs." In Season 1's The Big Bran Hypothesis (2007), Sheldon is seen pouring himself a cup of coffee and adding milk to it.
While the guys are discussing ways to improve manufacturing Penny Blossoms in Penny's apartment, the number of blossoms on the table in front of Penny keeps changing.
When Penny places her box of rhinestones on the kitchen counter it is opened but when Sheldon starts explaining how a business model works the box on the kitchen counter is shown sealed.
When Penny tries to get the guys pumped up about doing another order of Penny Blossoms, Leonard's right hand goes from flat on his face to a fist between shots.
Penny states she made 156$ in one week, selling Penny Blossoms. She also states she can make about 20 Penny Blossoms a day, and her profit per Penny Blossom is about 50 cents. That means she couldn't make 156$ in a week. Even if she worked all 7 days, she would make about 70$ (7 days x 20 Penny Blossoms = 140 Penny Blossoms; 140 Penny Blossoms x 0,50$ = 70$).
When Leonard and his friends are playing the chess game with lasers and later eating pizza with lasers, they are not wearing protective eye-goggles. In other episodes in which Leonard has used lasers he has always been insistent on wearing protective goggles.