Disclaimer: I don't own Harry Potter but I wish I did.
Harry and Lupin are having a conversation in his office takes place sometime during Prisoner of Azkaban.
"Harry, I have something to tell you," the professor said. "I'm a werewolf."
"Are you fucking serious?!?!" Harry asked him.
"Yes I am fucking Sirius, but that is beside the point" Lupin replied.
"How is that beside the point I asked you if you were serious" the teenager replied.
"Oh. I misunderstood the question, but yes I am serious about being a werewolf" Lupin said.
-FIN-