As I was reading through this great site, I was inspired to send in my own:
I was waiting tables at a popular chain restaurant when a young couple in their late teens sat down in my section. They were very nice and after talking with them for a while, I noticed that the young man sounded as if he had just had his tongue pierced. I have mine pierced, so I know that for a few days afterward, you talk pretty funny because you can hardly move your tongue. This guy talked exactly like a post-piercee; I was so convinced I was right that, in an attempt to connect with them further, I asked him, "So, when did you get your tongue pierced?"
It was like I dropped a gigantic rock on the floor between us. The couple's faces fell and they stared at me. There was a beat, full of pointed silence, then the girl frankly replied, "That's just the way he talks."
In an uncomfortable moment under their stares, it dawned on me that I had just accidentally made fun of someone with a speech impediment. My eyes grew wide, and my apologies spilled forth. I wanted them to realize that I am not the kind of person that would intentionally do anything of the sort. I finally realized I was probably digging myself deeper, so I sincerely apologized one last time and took my leave. I continued waiting on them, giving them the most personable, stellar service I can offer.
Fortunately, by the end of the meal, they had forgiven me!
Share your gaffes in the comments.. I would love to read them!