I was showing my advanced class how to graph the quadratic function y = x^2. I had just plotted several points and drawn the parabola:
Suddenly, one of my students blurted out, "That's that uterus thing!"
The classroom erupted in laughter. I literally had tears in my eyes from laughing so hard. The student who had said it was laughing, too, but she didn't quite get the joke. As it turned out, she only knew what a uterus looked like from a diagram in her health book. A caring student whispered it into her ear and a look of realization washed over her face, followed by a flush of embarrassment. She took it well, though.
Afterward, I graphed a few more points, including (4,16) at which point I said, "This one goes up a bit higher on the graph...at the top of the pelvic bone."