Not my problem but a lady at work was telling the story...

Her husband was away and she was leaving for the weekend. He told her
to shutoff the well pump. Also, since the pump we would be off he told
her to take out the two fuses for the water heater.

She said that she took out one fuse OK, but while taking out the second
fuse it was arcing. Her husband told her that she was supposed to take
them out at the same time.

My question is why would there be arcing if one of the fuses is already
out?