The most recent entry on this list comes from Season 7. During an argument with his wife Bernadette, Howard finds himself out of answers and resorts to faking a heart attack (his alternative was suffering a real one) and instinctively grabs his right arm. His right arm! Now Howard gets a lot of flack from Sheldon about not having a PhD, and only being an engineer. But not knowing which side of the body the heart is on? It was only a throwaway line meant for laughs but some mistakes are too stupid to ignore - the guy has a Masters Degree from MIT, after all. Maybe Sheldon's constant intellectual patronising of the guy was pretty much right on the money.