"There's an E in potatoes," I said.
"Nuh uh," he said. "Remember? Dan Quayle got in trouble for spelling it with an E."
"No," I said. "He was spelling potato, singular."
He rolled his eyes and pointed out that to pluralize something means to "only stick an S after it."
Whatever. At one point in my life I thought that people like this should be put to sleep, but these days I'm older and wiser and less humane, and I think they should have to receive each other's forwarded e-mail instead.