On a very few occasions one has the possibility of making a really apposite silly comment. Such an opportunity should not be wasted.
I once met a young policeman who told me how he was on duty outside an expensive hotel in the West End of London when this appalling woman flounced out. "Constable!" she summoned him, "Call me a cab!" He wrestled with his professional conscience for a while, but knew that it was no use. "Madam," he replied, "You are a cab!" Then he fled from the scene before she could take his number. (I suspect this might be a Groucho Marx joke: if not, it certainly ought to be)
By contrast, I missed my chance when I was going round Chatsworth House with a friend. Down in the basement there was an exhibition of servants' costume through the ages, mounted on tailor's dummies. The dummy with the postilian's uniform had broken and fallen over. I said to my friend, should I go up to the attendant at the door and tell him that his postilian had been struck by lightning? (following the legendary entry in a tourists' phrase-book from a previous century, "My postilian has been struck by lightning"). I approached the man, but before I could open my mouth he shot me a glance so savage, and so indicative of not understanding recondite jokes, that I lost my nerve and left the room in silence, to the accompaniment of cries of "Boo! Chicken!" from my friend. This was entirely justified on his part, since I doubt if I will ever again have an opportunity to use this memorable phrase.