There was a guy snorting smarties in one of my classes in high school. I'd mash em all up, he'd snort em.
I had a friend who always had all the good pain killers, so we mixed some of those in, mashed em up, gave em to the guy, and he got fucked up.
Went to the front of the class, grabbed a crap ton of those brown chemistry lab "paper towels" and started scrubbing the hell out of his forearm.. Dry rubbing hard, made it red and raw.. We asked him what he was doing, and with a very serious look on his face, while still scrubbing, he said "My arm... Its dirty..." and continued to scrub.
I guess you had to be there, it was funny as hell. In hindsight, glad we didn't kill him.