I don't know why I remembered this, but here goes ... At school in Edinburgh in the 60s I was in the CCF shooting team. One day we were shooting our .303 SMLEs on the open ranges at Dreghorn. I had finished my shooting and was sent to the butts to operate the targets. After an hour or so it was time to pack up and go back to school. For some stupid reason which I've never been able to explain, I unplugged the two-pin plug which connected the hand-cranked field telephone with the firing point. I put the plug in my mouth, tapped a friend on the shoulder and said: "Watch this ..." I then wound up the crank. I'll never forget the blue flashes in front of my eyes, the smell of singed flesh and sheer look of horror on the faces of my schoolmates. My actions may have had something to do with the quarter bottle of whisky we had smuggled into the butts earlier. Thank god the officer IC never found out. I had the burn marks on my lips for weeks ...
In the chemistry labs one day we forced an unpopular fellow pupil into a fume chamber, closed the sliding glass front, and watched him stare in horror at the flask which was happily bubbling chlorine gas (if I remember correctly) into the chamber. We let him out eventually ... happy days!