Continuity errors are part and parcel of creating anything that lasts beyond a couple of season. Just ask the Friends writers, who clearly didn't keep track of what they were writing for Ross particularly well, considering the sheer number of Annoying Mistakes In Friends that made it onto the screen. Unless you have a continuity checker working tirelessly to make spider diagrams and pool all the biographical information together to make sure no-one ends up having their appendix out three times or something, like the Rugrats team actually did, it's likely you're going to lose track of some of the major and minor events that have happened in the past to your star characters. But the internet won't keep track - not for minor life events that happen multiple times, or even for character quirks that fundamentally contradict what we've already seen, so sooner or later, you're going to get called out. With The Big Bang Theory now iadvancing into Friends-like numbers of episodes, it seems, like the show it effectively replaced, that the geekiest show on TV is full of similarly annoying continuity and internal logic errors. These mistakes go back as far as the pilot, but the major one can be forgiven as a case of the character not yet being completely decided upon. Because, frankly, the Sheldon we see in the pilot has very little correlation to the one who we all know and love now: he was called "practically an expert" at masturbating, despite his lack of sexuality since then, and he even makes a vague play for Penny's affections. That's just creepy, but that mistake is forgivable in comparison to the following annoyances...
18. Howard Would Never EVER Be Allowed In Space
In "The Russian Rocket Reaction" in season 5, Howard realises his dream of going into space, when he is chosen as a payload specialist, in probably the most ridiculous NASA decision in the history of the organisation. Because, frankly, there's no way Howard would ever be allowed into space, if his characterization over the previous four seasons is anything to go by. Among the many ailments that would rules him out are his asthma, a debilitating allergy to peanuts, almonds and walnuts (the Russian space programme is big on nuts for their nutritional value), his sea-sickness, his incredibly high genetic risk of heart illness, and his transient idiopathic arrhythmia. He's also a weed, but that's got to come lower down on the list. That's not to mention the fact that he clearly doesn't survive NASA's rigorous training schedule, which effectively breaks him, and forces his mother and fiancee to come and look after him (as if NASA would miss THAT.) Or, come to think of it, the fact that he is ruled out of taking part in the new Defense Department laser-equipped surveillance satellite programme on security grounds, as he is denied the requisite clearance. Which NASA clearly conveniently over-looked.