Factual error: The main apartment in the show is located in Pasadena, Calif. When looking out the window in the background, mountains are shown in the distance and far away. In reality, Pasadena lies right underneath the long mountain range so the mountains would be up close, not far away.
Factual error: Every time we see Leonard's laser lab the door is open and he is able, if the story requires it, to fire the laser. As evidenced by the several safety notices visible and the scripted requirements for characters to put on safety goggles it should not be possible to activate the laser while the lab door is open - it would be interlocked, meaning the laser wouldn't function unless the door is closed.
Factual error: Characters sometimes talk to one another on video calls, and a character (A) often watches these from an angle rather than face on, allowing the viewer to see both character A and the character on the call (B). When this happens, character B is shown turned a little to one side, to give the impression that they are looking directly at character A (as they would be if they were present in the same room). In reality, this means that character B is looking off to one side of their monitor and not at the image of character A, something that it makes no sense to do. No matter what angle the laptop is shown from, provided character B is visible, they should appear to be facing the viewer.
Factual error: Sheldon has a rigid schedule. Halo Night is known to be on Wednesday night. Penny sleeps on the couch in Sheldon and Leonard's apartment. The following morning, Sheldon cannot watch Doctor Who on BBC America because Penny is sleeping on his spot on the couch. He states that he has been watching Doctor Who every Saturday at 6:15 a.m. The following morning should be Thursday.
Factual error: The time machine in this episode is supposedly the same one used in the H.G. Wells movie, but there are mistakes in the controls that would have been obvious to the characters: 1. When Leonard first gets into the machine he talks about traveling into the past and says something like "I'm setting the date to..." That is the method used to operate the Wayback Machine in the Rocky and Bullwinkle cartoon, but not the time machine in the H.G. Wells movie. Rod Taylor could not set the desired date on the controls, he simply used the lever to move forward and backward through time and the date display updated automatically to show the current date. 2. In the movie the default position of the lever was at a 45 degree angle. Pushing the lever forward moved the machine into the future, pulling back on the lever moved the machine into the past. In the TV show the default position of the lever is vertical and Leonard pulls the lever backwards to move forward into the future - opposite of the movie.
Factual error: Raj and Sheldon are watching TV in Raj's apartment and we hear music playing. Sheldon asks if the woman on TV was Aishwarya Rai to which Raj says yes and then they argue about her and Madhuri Dixit. The song playing was from the Bollywood movie Kaho Na Pyar Hai, but neither of them are in the movie - the lead actress was Ameesha Patel. (00:14:50)
Factual error: Leslie Winkle takes shelter with Howard in the middle of a paintball game. Her gun has no hopper for paintballs and thus no ammo, so it's useless, despite her apparently using it outside seconds earlier. This isn't a model with an internal magazine - the port to attach the missing hopper is plainly visible.
Factual error: Sheldon says the movie Gremlins "baffles" him in regards to the instructions being very clear."Don't feed the gremlins after midnight." However, this instruction is only for caring of a Mogwai, not gremlins (the gremlins are formed by Mogwais eating after midnight). Sheldon, of all characters, would not mistake Mogwais for Gremlins and he would know the exact wording of the instructions.
Factual error: Sheldon's voice becomes squeaky when helium is pumped into his office. But if the room contained enough helium to make his voice squeaky just by breathing, Sheldon would actually be suffocating due to lack of oxygen, the lighter helium having displaced the heavier oxygen. You can do it with a balloon because you can breathe normal air between huffs, but if you're in a room full of helium, you won't last long before passing out and asphyxiating.
Factual error: In order to get vengeance on Kripke, Sheldon mixes a solution of hydrogen peroxide, saturated potassium iodide and liquid soap, creating a large foam blob. This is easy to replicate, and what you will get (and look carefully, it is what Sheldon gets) is a huge, aerated foam mass consisting almost completely of bubbles. It is barely heavier than air, and if dropped from a ceiling as we see later in the episode it would float harmlessly about the place. Whatever it is that drops on Kripke and his visitors later, it isn't the foam mixture we see earlier - it looks like some sort of custard mix.
Factual error: The foam Sheldon used on Kripke consists of mixing ordinary dish soap, hydrogen peroxide, and saturated potassium iodide. That kind of exothermic reaction is dangerously flammable, so it should have severely burned Kripke and the members of the university board when it fell on them.
Factual error: At the very end of the show, Leonard and Raj arrive at the hotel, which is supposed to be in Geneva, Switzerland, to visit CERN. If you look out the "hotel" window, it looks like they're half way up Matterhorn, but in Geneva there are no big/rocky mountains anywhere near the city itself.
Factual error: Sheldon and the team are league bowling and have a match with Will Wheaton's team. They are bowling on lanes 2 and 3. In league bowling, you have to bowl on lanes that start with an odd number because the ball return is shared between those lanes. In league bowling, you take turns with each lane so that any differences in the lanes evens out, and this lane layout wouldn't allow that.
Factual error: During the final scene of this episode, Sheldon steps out of his office wearing a gas mask and engages Leonard in conversation where he then states he is making hydrogen sulphide gas (more commonly known as H2S). Leonard correctly identifies this as highly flammable. However, this gas is far more dangerous and is harmful to the human body at as low a concentration as 20 parts per million (ppm), can cause permanent damage at 100ppm and is fatal after two breaths at 500ppm. So for Raj (and his bird) to be completely unharmed in a high concentration of H2S (noted by the fire) is impossible.
Factual error: Howard's claim that characters in World of Warcraft can engage in sexual activities is wrong, also while there is a Bridge of Souls currently in the game, there is no way to get under it.
Factual error: Amy is sitting outside a liquor store that shows a sign indicating it is open 24 hours. However, that's a crime in CA. Any on-sale or off sale licensee, or agent or employee of that licensee, who sells, gives, or delivers to any persons any alcoholic beverage or any person who knowingly purchases any alcoholic beverage between the hours of 2 o'clock a.m. and 6 o'clock a.m. of the same day, is guilty of a misdemeanor.