Many years ago, together with others, I was hosting some visiting Belgian Air Force aircrew at Brize for some air show. Most of the Belgians sported significant moustaches...
"Why do they all have moustaches?" asked some rather young person-formerly-known-as-a-WRAF Plt Off who was sitting on my knee.
"Perhaps they just like the Velcro effect", I told her.
"What's that?", she innocently replied.
"Think about it....."
About a minute later she suddenly went bright red and clapped her hand to her mouth, before giving me a thump on the shoulder.
"Penny's dropped, I guess?" was my response.