It doesn't happen often, but when it does, I try to laugh it off.
The only time I can remember being humiliated was in 5th grade. We had some stupid "American Idol" thing in Math class where people in the class would sing math-themed songs. My friend and I were in charge of the halftime show thingy.
We decided that it would be funny if he said something along the lines of "Now we're going to have a nice, normal, comedy show.", and at that moment, I would come out of nowhere to sing Peanut Butter Jelly Time.
It was all going as planned until someone on the stage behind the curtain tripped me mid song. That was the last time I ever did anything like that in front of a group of people that large.