If you have ever faced an angry Vogon, you are likely to be a Vogon yourself. But if you have had the misfortune of facing an angry Vogon while not being one yourself, what you will remember, if you survive the meeting long enough to remember anything, is the saliva.
During a Vogon argument, the amount of expelled saliva is such that one finds himself wondering where the body finds all that water and why if it does, it can manage not to end up dehydrated at the end of the aforementioned argument.
Arthur Dent, Ford Prefect, Zaphod Beeblebrox and Slartibartfast would remember the saliva.
And they would remember the impending danger of being thrown overboard by a furious Prostetnic Vogon Jeltz into the void and into the Gnab Gnib. You may know that the Universe is collapsing into a big dreadful Nothing, but you can't help yourself but from not wanting to be thrown into it by a nervous, ugly creature.
What they would also remember is seeing the said creature being sent to meet its Maker (and if it is to be taken literally, keep in mind that the Maker in question would be too ashamed of that part of His creation to ever want to meet it) by a robot before they could even think about getting hold of their towel.