Not a mechanic related embarrassment but embarrassing nonetheless. Working as a welding apprentice I was given the job of cutting a chain sprocket off of a drive shaft. Over the top of the sprocket was a guard which had a nylon runner underneath. The way the shaft was positioned I had to cut it from under the guard.
Here’s me using an oxy/acetylene torch, 1/2 way through the shaft the nylon started to melt, unfortunately it ran down the guard and on to my forehead.
It took just over a month for the burn to heal which was The size of an Australian 20 cent piece.
Least to say the nicknames were: Spot, Ding-dong, doorbell etc…