I assume, terrier, that it's for the same reason that the plug is IN the bath of water. If the plug was on the outside, pressure would force it out. But I'd have thought that, for health, safety and hygiene reasons, there would be an easier way of draining the vat than sending a worker in to pull out the plug. Did he take his boots off first? Had he washed his feet? Did you chocaholics know that sweaty workmen had been wading through your chocolate before it was cast into bars and wrapped?

I see the man concerned was 21 years old. Was he a new apprentice, and was this some sort of ritual, like sending the new boy for a left-handed screwdriver or whatever? "Just wade into this vat of chocolate and pull the plug out, boy!" and the rest of the shift stand around laughing their socks off (or the rest of the sock laugh their shifts off, whichever you prefer)

Are workers in chocolate allowed to wear socks?

You're right, there has to be a song in this.

Andrew