8. The Schedule Problem
Sheldon is a creature of habit. More than that in fact he is rigidly locked to his schedule, which makes his dalliance with allowing his life to be governed by the roll of a dice even more hilarious. So perhaps he should have known that in The Dumpling Paradox, when Penny sleeps on the couch in his apartment, and he wakes up to complain that she is interfering with his Doctor Who watching (as he does "every Saturday at 6:15am) that he has his days completely mixed up. The night before, after all was Halo Night, which falls every Wednesday, and not Friday.
7. Leonard Was At Comic Con And At The Arctic At The Same Time
According to two separate Big Bang episodes, Leonard was enjoying two major, life-changing events at the same time during the summer of 2009. As established at the end of the second season, Leonard heads to the Arctic on an expedition with Sheldon, Howard and Raj, where he and the latter two wrestle with the urge to murder Sheldon. You'd think Leonard would remember that, since his return coincided with Penny's realisation that she wants him. However, in Season 5 episode "The Good Guy Fluctuation," Leonard apparently completely forgets about the Arctic and reveals that in the summer of 2009, he went to Comic Con, dressed as Lion-O, and Jim Lee commemorated it with a personalised sketch.
6. Sheldon Should Be Dead And Is/Isn't Allergic To Cats
One of the biggest mistakes in The Big bang Theory's catalogue of Sheldon-based errors is that the idiosyncratic genius should be dead. ] In "The Vengeance Formulation" in Season 3, when Sheldon makes a radio appearance, he is pranked by Kripke, who pumps helium into his office, which changes his voice hilariously, despite the fact that the volume needed to have such an effect would have killed Sheldon thanks to the lack of oxygen in the room. But then, that prank would have been a lot grimmer. And then, that episode's commitment to prank science is completely wrong anyway, since Sheldon's reciprocal prank involves mixing a solution of hydrogen peroxide, saturated potassium iodide and liquid soap to make a giant foamy mess. The result gloops onto Kripke and his guests looking a lot like thick gravy, and not the light aerated foam that would actually be made by that solution (as happens when Sheldon demonstrates the mixture to his friends.) Also, that Helium scene isn't the only time Sheldon dices with death, since it is established early on that he's allergic to cats, but then later, when he loses his job and his mind, he adopts a frankly insane number of them, and keeps them in his room.