I am new here as I only recently, by way of my wife, became a fan of BBT. Great show. Sheldon is by far my favourite.
Anyway, with that in mind I thought of a episode concept that I REALLY hope they use because I think it would be hilarious. I am sure you have all heard stories of the random innocuous dude somewhere who works some entirely too ordinary 9-5 job (like a postman or mechanic or whatever) who also just happens to be insanely smart. Whether this is more urban myth than truth is up for debate (I prefer to lean toward the truth side), but these so called people are usually high level members of genius societies, knowing far more than someone in their profession should about completely unrelated topics and possessing advanced degrees in seemingly random subjects. This is the sort of dude that needs to use in a Sheldon centered episode.
Summary: Sheldon meets a completely ordinary person who turns out to be smarter than him. His attempts to sort this out end badly and entertain his friends to no end.
Detail: I imagine it going sort of like this: Sheldon goes out on some business, complaining about some inferior mind and how they know nothing and he knows everything, basically being his egotistical, superior self. Then, random mailman dude tromps by doing his job and just happens to overhear Sheldon doing his thing. He stops, interrupts Sheldon and gives him a piece of his mind. Sheldon dismisses him as a know-nothing but the fellow persists and challenges him. They soon begin a heated conversation that evolves into a discussion on some very cerebral topics. They then part ways in complete disagreement on all matters discussed.
Sheldon, now worried, investigates the various things discussed and discovers, much to his horror, that the mailman was right (in most cases). He then drives himself mad trying to figure out how this is possible while complaining to his friends about this strange encounter (much to their extreme entertainment). Furthermore, he tries to find this mysterious mailman again (whether he does or does not find him could be an interesting subplot) to get the answers he desires. What you do with this at this point is up for debate (I imagine Sheldon's head exploding somewhere in here).
Thanks for reading!