When Leonard is asking Penny out to dinner, her door changes position several times between shots.
Using the laser to heat her noodles in 2 seconds is not possible. It would take roughly an hour for her noodles to increase 50C degrees. The output of a laser needed to heat the noodles in 2 seconds is far greater than the output of her laser.
Oxygen-iodine lasers do not exist with a power output of 500kW. The biggest are around 50kW - one that powerful would take up most of Leslie's lab. Lasers of that type are used by the military for knocking down missiles.
Leslie uses a 500 kilowatt oxygen iodine laser to heat a Styrofoam cup of noodles. This laser would have drilled a hole through the Styrofoam cup causing the liquid to leak out.
Leslie's laser could not have been an oxygen-iodine laser, as even a small one would be much bigger than the laser on her bench.
Leslie's laser could not have been an oxygen-iodine laser, as they emit in the infra-red part of the spectrum, thus the beam would have been invisible, not red, as is shown. Her laser is most likely a helium-neon laser, with a power output of 100mW, at most, and completely incapable of heating her soup.
When Leonard uses the glass to pick up the olive, it falls out of the glass and clearly goes behind him away from the table. Yet, he goes under the table to search for it.
When the (supposedly smart, game-loving) guys are playing Jenga, they are not completing each top layer like they are meant to.
Leonard the genius says he's going to go 'lay down' due to the possibility of having a concussion. The proper term is 'lie down'.
in this episode Leonard refers to Sheldon having asthma, while later in the series he himself is the one suffering from the condition.
Howard (Simon Helberg) brings Sheldon (Jim Parsons) to a dancing class, however, in a later episode, he says he does not enjoy dancing and never will. Then, in the fourth season, he reveals that he can do formal dances such as the waltz.