I am not unfamiliar to putting my foot in my mouth. I've done that many times, I've actually done that the first time J came up and spoke to me. And then of course, I get amused when other people put their foot in their mouths, and I walk away wondering if they actually realised it. For example, a conversation I had with the cashier at Nordstorm Rack yesterday:

Cashier: Where are you from? Me: Singapore. Cashier: Oh. You don't look African. Me: It's not in Africa. We're in Southeast Asia. Cashier:  Oh. You don't look Chinese. Me: -head meets desk-