Anorak

Train noise
William: Oh, there goes another train!
Wang Fei: What do you mean, another train? It was a D5900 Class diesel-electric locomotive, the last one in operation.
William: Erm, ok.
Wang Fei: And due to arrive at 1203 is the Class 170 "Turbostar" British diesel-multiple-unit train from Edinburgh.
William: Great.
Wang Fei: You don't sound very interested.
William: I'm not. You do realise that you are a complete anorak when it comes to trains, Wang Fei.
Train noise
Wang Fei: An anorak? That's a kind of coat! Yes, I'm wearing an anorak, but I'm not a kind of coat, William, I'm Wang Fei!
William: Yes, well the word anorak is used to describe people who have an obsessive hobby about something that not many people are interested in.
Wang Fei: I see. You mean a hobby like train spotting?! But I thought everyone liked it?
William: What's so interesting about standing in the cold, waiting for rare types of train to arrive? The only trains I'm interested in are the ones which get me from A to B.
Examples
He is a total anorak. He always stays in and watches Star Trek.
My friend is a bit of an anorak when it comes to dance music. He knows every DJ and every track, when they were published, how high they got in the charts. I prefer just to dance to it!
Wang Fei: So you really don't like trains?
William: Oh, I don't mind them, Wang Fei, I just don't find them that interesting. And it's so cold in this country that you need to wear that huge anorak while you wait for them, which is where the phrase came from.
Wang Fei: You mean, people like me, waiting for trains in my big anorak?
William: Yes, exactly—that's it.
Wang Fei: So if this phrase exists, it must mean there are lots of other people like me?
William: Well, you don't see many. Maybe you could try a trainspotting website.
Wang Fei: Hang on. Is that ... I think there's someone at the end of the platform in a long coat, with a clipboard ... looks like he's waiting for a train!
William: Oh, well go and say hello, then.
Footsteps
Wang Fei: Hello, are you waiting for ... 
Anorak: The Class 170 "Turbostar" ... 
Wang Fei: British diesel-multiple-unit ... 
Anorak: From Edinburgh, due to arrive at 1203 ... ? Yes! And your name is?
Train noise
William: Well, I don't know. Whatever makes you happy! Bye from me.