Me: "So you want to be very careful when you're setting up this part of this experiment, because it can be challenging to gauge when the first pendulum comes to rest after transferring its energy to the second -"
Student #1: "That's a cool piercing."
Me, caught off guard: "What?"
Student #2: "In your tongue."
Me: "Oh! Er, thanks. Um, so, you should probably spend all of tomorrow on this section of the experiment."
I told this story to a colleague. He rolled his eyes and responded, "They didn't hear a word you said."
In conclusion, I may not be the world's most effective physics teacher for 18 year old males.