Green slime.
There was a school assembly about how smoking is harmful. They taught us about the Cilia, little hairs inside the lungs that keep foreign objects out.
They wanted a volunteer to come demonstrate what happens to the cillia when you smoke. They asked for someone with a good sense of humor so I volunteered.
They called me the very silly cilia and dumped this green slime on me. The rest of the students were expecting humor so I started punching the slime that dripped off of me. The students enjoyed it.