This is a nasty one we used to pull on new hires years ago.
Back in the days when smoking was allowed in the workplace we would run a tube from an adjacent workstation to the inside of an oscilloscope.We would task the new hire with making a simple measurement using the scope.
We would wait until the new hire was hard at it and then one of the smokers in the lab would blow cigarette smoke through the tube.
You can imagine the new hires horror his first day on the job when he saw smoke pouring out of an oscilloscope he was working on.
Back in the mid 1960's I was working as a design engineer in an integrated circuits goup at one of the major IDM's. Smoking was allowed and I did at that time. We had a secretary who typed up all our reports and memos on an IBM selectric typewriter. It was quite modern at the time but sometimes the type ball would stick and the secretary would open the lid and smack it on the side to get it going again. I noted this and wired up a normally closed foot switch on the AC to the typewriter and positioned it under my desk. I could casually hit the switch and kill the typewriter then turn it back on as soon as the secretary opened the lid and looked in to see what was wrong. This was fun for a while but then I decided to train her that the typewriter would only work with the lid up. That took only a couple days. Training her back to believe it only work with the lid down took a little longer! We finally tired of the game and ran a plastic tube into the typewriter for the "smoke test". I stopped the typewriter with the foot switch and blew in the smoke as she opened the lid. It took a couple hours to convince her to try the typewriter again! She eventually found out and got even by taking all the handles off my heavy desk drawers and closing them tightly!
Let me guess. Then the manager walked by, saw the scope going up in smoke and fired the new hire because the smokers hid and did not admit it was all a joke and get themselves fired. The company went through dozens of new hires until the company banned smoking to lower their health care costs and the smokers had to now go outside to smoke. The smokers still got the new hires fired because the FNG didn't smoke and did not go outside and join the smokers impromptu meetings thus not getting along with his coworkers ;-).
In school we would have impromptu lessons on what a capacitor is for new students. In fact students who took this “lesson” learned real quick the difference between a small cap and a large electrolytic cap by the sound of the pop or even the amount of insulation that came out after they were discharged. We had a few good laughs after leaving a fully charged 100uF cap innocently on the lab bench next to their breadboard.
Technical Market Manager, Tektronix
Back when we were making hi-fi power amplifiers, we would attach a 1/4 Watt resistor across the load resistor on the back of the work bench and then a firecracker fuse to that.
That combination would really create a nice surprise !!
This reminds me of the time when we were using titanium tetrachloride to produce smoke trails for tracing airflow. One night (very late) we were struggling with an overload requirement for a power supply. At about 1 am we heard the chief engineer approaching so we dripped some titanium tetrachloride onto the power transformer. When the chief engineer entered the room we said "Larry we solved the overload problem". You should have seen his face when he saw all of that smoke pouring from the power transformer.
My first day on the job they sent me to the bakery over the road to buy custard slices. These were really nice, but covered in icing sugar and had to be eaten carefully - if you breathed in while biting, your throat got covered in icing sugar and you started choking and coughing. Which the new guy always did. Much to the amusement of the old hands.....