Weird version:
"Didn't you say you wouldn't abandon me?"
"Sorry, I'm a Slytherin, and you're not."
"You care about..."
"Of course."
Comedic version:
"Are you even a Gryffindor? You go to Slytherin every day. You're a traitor!"
"You're just jealous that Slytherin won't let you in. Hmph!"
