I had a look today through a new Turkish supermarket which opened very recently near my work, just browsing through the shelves, seeing what kind of things they sold.
Behind the cash registers, there was a little bakery area, and I had a look there, too, at the various baked goods they sold.
A sign caught my eye, saying "kurabiye"—"Ah! Presumably, the source of κουραμπίεδες! I should've thought that word might have Turkish roots."
Then the young lady behind the counter asked me whether she could help me, and I replied that no, I was just looking around.
She seemed a bit surprised that I could speak German, which surprised me: had she expected me to speak Turkish?
But no—she had heard me speak English to Amy, and so she had expected me to speak English (or, I suppose, accented German).
Then she asked me why I spoke English to Amy, and I said, to teach her—as my father taught me.
She also seemed to think that Amy only spoke English, but when I said that Stella spoke to her in German, she was intrigued: a child that grows up speaking both English and German!
She herself was born in Turkey and grew up here, and speaks both Turkish and German. So that's not really all that different, is it? Yet she seemed a bit impressed.
I also asked her where she had heard me speak English to Amy, since I didn't recognise her. She said, on the bus every day, as she went to school.
So: people watch you and listen to you, even if you don't notice!