Spooning and forking

Lecturer: (speaking of Valimar Nabokov he of Lolita fame)

"I told him about a nun who sat in the back row of one of my lecture courses, and who one day complained after class that a couple near her were always spooning." 

‘Sister,’ I said, ‘in these troubled times we should be grateful if that’s all they were doing.’ ... 

‘Ohhh,’ moaned Nabokov, mourning my lost opportunity, clapping his hand to his head in mock anguish. ‘You should have said, “Sister, be grateful that they were not forking.’