I used to get a bit non-plussed when working at places with an obvious uniform (Pizza Hut, Burger King, Somerfield etc...) and getting asked "Do you work here?". No, I just like the uniform!?!?!?
Saying that, when I worked in Somerfield (I believe it's moved now Naz? When it was outside the station), they used to pick up people on Saga trips outside and we had a similar uniform to the Saga reps so used to be asked all kinds of random things.
I once got asked if we served Pizza, whilst working in Pizza Hut and would regularly be asked for a Mcthis and Mcthat when working in Burger King.
When working in a library, had someone ask me to find a book they wanted. The only thing they knew about it was that it was blue!?!
It never ceases to amaze me!