Well. When I was a Freshman, I had the brilliant idea to snort Poprocks before Choir. You can only imagine how strange that felt, having your sinuses snap, crackle and pop.
When I was a Junior, in AP English, my teacher mentioned homework, and my immediate response was, "Shi-," except spoken completely. I hadn't realized I'd said with plenty of volume until the class erupted in laughter. My teacher had this look of shock/amusement on her face. It was beautiful.
And years ago, at my friend's old high school, some stoner kid let a cow (this is pretty much in the boonies) into the school. What fun!