After many unfortunate events involving lost baggage, my parents always travelled with a few spare clothes (esp jocks and socks) in carry-on luggage, and my mum also carried some washing powder in a ziplock bag.
When we got to Bangkok Airport in 1993, the security guards took exception to this bag of white powder. One opened it, licked his finger and put some on his fingertip, and tasted it.
He made a face that can only be described as "dear god, that really was washing powder" and let us all through while his colleagues laughed...