I do have a reputation for knowing the usually-useless stuff. My younger sisters in particular think that I know everything that there is to know about almost everthing.
Now, my sister Jess is very earnest, smart and well-meaning, but she can be more than a little bubble-headed.
About six months after she moved out on her own, I got a phone call from her. She gave me the usual how-are-yous, never seemed like she was in a rush or anything, then casually threw into the conversation:
“Hypothetically, what would you do if you had an oven fire?”
Knowing my sister as I do, I immediately asked “did you turn off the oven? Can you, without getting burnt?”
“Oh, yeah - Hang on a second!” she said. “There, now it’s off. So, hypothetically, what is it that you would put on a grease fire that is contained in the back of the oven?”
I had that happen almost idetically – only it was a lock on a door for which you had to punch in a code. We were supposed to have a class in a computer room, but the computer guy, in a snit (he hated our prof), added the punch code lock (the kind with silver buttons numbered from 1 to 5) so the class couldn’t be held there.
The prof sent one student to go beg security to let us in, and someone else asked me “You know how to get passed these, right?”
I shrugged. I mean, what kind of hooligan do they think I am? You think I can just magically concoct the correct combination? Puh-lease! No way.
While we waited for security I idly punched in the code to my faculty’s lounge – nope, didn’t work. Then I idly punched in the code to my mom’s office – by crazy and highly unlikely coincidence, they’d used the same combination. It worked, we were in.
Suddenly everyone looked at me in awe as if I’d been revealed to be a notorious cat-burglar who could crack any safe.
Yes, saramamalana, that was what I had in mind. 
Bibliocat, I was thinking of this thread while I was sitting in the pharmacy yesterday reading a magazine about—of all things—wave mechanics for an artificial outdoor surf park. This information will never be useful to me, but it was interesting, and now I just know someone will pop up with a question in my presence about how it all works.
You may wish to read up on Richard Feynman, Eats_Crayons. He garnered the same reputation as you and I, on a much larger scale, while working at the Los Alamos facility where he and other scientists were trying to develop the atomic bomb! Try the book Surely You’re Joking, Mr. Feynman for that great story.
I am regarded by my family and friends as having encyclopedic knowledge of nothing very valuable. I’m always ready to throw in a reference to the Treaty of Balfour or U.N. resolution 242 in a disccusion of the Middle East, for example.
But the one thing that astounds, ABSO-FREAKIN-LUTELY ASTOUNDS my kids is that I can figure out the tip for virtually any tab in my head.
How do I do it, they ask. I keep giving them the same answer. Divide the bill by 6. If you want a cheap tip, divide just the total. If you want a normal tip, divide the tax and total. If you want to be exceptionally generous, divide by 5.
For some reason, they don’t get it.
Heh. And I thought I was the only one who was expected to know everything. My husband certainly expects that of me. What really gets me is when he asks me science and math-related questions, which he knows damn well I know nothing about. My answer has become, “What, do I look like a rocket scientist/mathematician to you?”
Work is no better. I’m the official dictionary/thesaurus/grammar expert. Believe it or not, I have to look things up once in a while, too. I had to look up “mathematician” for this very thread, as a matter of fact. Once my mom called me at work to ask me how to spell something. I told her, then went out and bought her a dictionary.
My friends don’t necessarily ask me questions, but often act like they think I’m smarter than they are, no matter how hard I try to convince them otherwise. I think it all stems from the time I randomly answered “Rekjavik” to a final Trivial Pursuit question I had no clue about and got it right.
Apropos of nothing, yellowval, my mom answers “Sandy Koufax” to any Trivial Pursuit question calling for a person she doesn’t know. She’s been right several times.
Yes, that’s it exactly! On one hand, you have the thought of “Why would the average person care about wave mechanics for an outdoor surf park?” On the other hand, that does sound rather interesting, and I, too, would probably read it.
And some nugget of information about it would lodge in my brain and pop up years from now, and I’d have to stop and think, “Now, why do I know that?” :::shrug::: “I musta read it somewhere” 
But I think on some sub-conscious level, you did know the answer was Rekjavik, and that’s why you said it, rather than saying “London” or “Nashville.”
I’ve done that, too. I’ll think I don’t know an answer, and say what I think is a guess, and it turns out to be right.
I thought my mom was the only one with a stock answer to those - hers alternate between Jimmy Carter and Richard Nixon. Always said in a very triumphant voice, like she’s positive that the population of Outer Mongolia will actually be Jimmy Carter or Richard Nixon, and she’s put something over on us.
And yeah, I read the encyclopedia, dictionary, Childcraft, and everything else I could get my hands on as a kid (still do - Mom’s kept the Childcraft subscription active for me all these years!). Everyone always wants me on their trivia teams, and I’m the one who gets all the obscure questions.
Same thing with me. Then when someone is able to prove me wrong with something, everybody turns to me and goes “HaHA! YOU were wrong!!” like I’m not human and am not allowed to answer a question incorrectly or not know something. Annoying.
Of course, it didn’t help when one time I answered a Final Jeopardy question (answer?) correctly based only on the category name. And it wasn’t obvious.
My parents advocated looking up the answer to a question, and not being an athletically gifted child made books a friend early on.
Working for a bank equipment company years ago, I was the guy sent to other regions when problems arose. One assignment was to train new video installers and handle a backlog of service calls. We had to get a video camera installed in the lobby to cover the ATM (front of the bank) but the VCR, switcher, and everything else was in the rear. In between was 50’ of interlocking grid tile ceiling and only two feet above it. These ceilings aren’t weight-bearing. We could get above the ceiling in the lobby and the rear, but traversing the in-between was the challenge. After a trip to the hardware store, and a sporting goods outlet, I took a 1/2" hex nut, tied it to the end of a roll of masons line, and shot it across the ceiling using a slingshot. Then, the masons line was used to pull the CCTV cable across the ceiling.
We returned to the branch office shortly after noon, and the manager assumed we’d given up. The fellow I was training pointed to me and said something along the line of ‘McGyver figured it out pretty quickly’.