This is an experience which happened a while ago, but I still find it amusing.

I work with a black girl. She is very friendly, cockney-ish accent (raised in London) and kind of pretends to be dumber than she actually is at times which catches a lot of people off guard if they are biased/stigma. Anyway, one day, we were having group meeting and part of this she started mentioning about the transition from her home country when she was little to the UK. As you can imagine, people were curious, pondering which African country and people were wondering since she has never spoke about this before (We simply thought 'London born and raised'). Admittedly, I was thinking United States or maybe Caribbean islands at this point. One person finally asks, "Just out of curiosity, which country are you from?" and she replies, "Oh, I am from Austria." and the room just went kind of deadpan silence because no one remotely considered that country. You would think to cover up the embarrassment, the subject would be changed, but the person who asked kind of said "Well, I have to admit, I was thinking of somewhere like Africa where you were from." which made it even more cringeworthy.

Good story about making assumptions can be bad.