The Pork Chop Indeterminacy - S1-E15
Corrected entry: Sheldon asks Missy why she doesn't tell her friends that he is a toll taker on The Golden Gate Bridge. There are no toll takers on the Golden Gate Bridge. Tolls are paid by credit or debit card, a prepaid account or by invoice to the registered car owner's address. There is no way Sheldon would not know this.
Correction: Sheldon was just suggesting that being a toll taker or something of that profession is as ridiculous as her telling everyone he was a "rocket scientist." Even if the statement was indeed true it doesn't affect my point.
Correction: S1-E15 aired in May, 2008, but the Golden Gate Bridge didn't switch to all-electronic toll collection until March 2013, and the decision to convert to electronic toll collection wasn't made until January, 2011.