"Is there really that much merit in merely existing, Pads?" Remus asks with a small smile, green eyes twinkling with amusement. Then he shifts and clears his throat. "I mean, professor Black."

He's not really being insolent on purpose. It's just that Sirius is still Sirius and it's hard to remember that he's supposed to show the same kind of respect to him as he would to professor McGonagall for example.

"Do you like it?" he suddenly asks, a little bit shyly. "T-teaching."