Well, I have a few things really. I can't decide which was the worst.
First, one time, I believe it was in 2nd Grade, we were learning about plural nouns. My teacher was talking about the irregular plurals like mice and children. So she asked me, "If the plural form of goose is geese, what is the plural form of moose?". Since I wasn't expecting her to ask me, i stupidly replied, "Meese?" My whole class + the teacher started cracking up. It wasn't really that embarassing, but still.
Second, one time, me and my dad were walking home from some place. My mom said she would be gone when we got back, although she might be back by the time we did. I looked behind us, and I saw a car that looked a bit like her car. The car stopped, so I figured it was probably her. I waved to the driver and was about to get in when I noticed 1. that it wasn't my mom driving and 2. the car looked NOTHING like my moms car. I just stepped back, ran to catch up with my dad (who hadn't even noticed lol), and pretended like nothing happened.
And just for the lulz, back in preschool, I was angry at my teacher. I forget why, but I think it was because she gave me a time-out. She dropped something, and when she bent down, WHAM, I kicked her as hard as I could! That wasn't embarassing, persay, but I thought it was close enough.