At that point, I felt an importunate tap, almost a punch, on my upper arm, from Charles’ direction. I turned to him. He was sitting in a fairly normal position in his chair now, except that he had one knee tucked under him. “What did one wall say to the other wall?” he asked shrilly. “It’s a riddle!”
I rolled my eyes reflectively ceilingward and repeated the question aloud. Then I looked at Charles with a stumped expression and said I gave up.
“Meet you at the corner!” came the punch line, at top volume.
It went over biggest with Charles himself. It struck him as unbearably funny. In fact, Esme had to come around and pound him on the back, as if treating him for a coughing spell. “Now, stop that,” she said. She went back to her own seat. “He tells that same riddle to everyone he meets and has a fit every single time. Usually he drools when he laughs. Now, just stop, please.”
“It’s one of the best riddles I’ve heard, though,” I said, watching Charles, who was very gradually coming out of it. In response to this compliment, he sank considerably lower in his chair and again masked his face up to the eyes with a corner of the tablecloth. He then looked at me with his exposed eyes, which were full of slowly subsiding mirth and the pride of someone who knows a really good riddle or two.
Salinger, J.D. For Esmé – With Love and Squalor