Because references sometimes work best.

: Me": "What is 'montagne' in English?"
Learner: "Uh... I don't know."
Me: "The English word for it is 'mountain'."
"Learner: "Ah! Like the movie with thew two cowboys!"

Because reasons.

Learner: "I like easy-listening music because of reasons."

The phonology of the toppings is divine, too.

Learner: "The Napoli pizza is very different from the usual Italian pizza, because of the morphology of the pizza... "

You must've been a cutie.

Learner: "Oh, before, when I was child, my nickname was Gagarin."
Me: "Why?"
Learner: "Because when they took my picture, they say I looked like him in his spacesuit."

You're more of a conundrum, I think.

Me: "... And that's it for today. Do you have any questions?"
Learner: "No, I'm not a question."