As far as track fans are concerned, my wife sees them as ranging from almost normal (DJ, GH, myself occasionally) to anorak clad train spotters.
scarier than an anorak-clad train spotter are the (for lack of a better word) "airframe geeks."
I was once travelling between baseball games with some NBC types and while in the waiting area, one of their frequent-flyer cameramen pulled out a notepad and started checking the fuselage numbers on the planes outside:
"Ahh... 692-LTD; skidded off a runway at O'Hare in July of '87.... 411-XBY; left aileron came off between Dallas and New Orleans, August of '93...."
Only slightly unsettling!
(I'm sure there must be whole websites devoted to this kind of thing)