All inter-galactic travelers/hitch hikers know the importance of carrying a towel.
What the strag (strag: non-hitch hiker) will think is that any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still knows where his towel is is clearly a man to be reckoned with.
(from the Hitchhikers Guide to the Galaxy by Douglas Adams)
My parents have never read the guide nor are they familiar with the intricacies of interstellar travel. They are however quite particular about always packing towels.
Never have they reminded me to carry my tooth brush, yet they always ask if I’ve remembered to pack a towel. Often going to the extent of putting an extra one in – just in case! As a result I’ve sometimes ended up at my destination with 2 towels but no tooth brush or night suit!!