A very short parody (well, sort of) of the 'marriage/concubine/whatever contract' trope.
"Wait," said Harry, starring aghast at the girl lounging on his bed, "you're seriously telling me that my great grandfather won your virginity in a poker game, before your parents even met? That's insane!"
"Well," Lavender replied, "if you want to get technical about it, he won the virginity of the next witch to be born to House Brown, and that happens to be me. Won-won and I really want to take our relationship to the next level, but we can't do that while I'm a virgin. So, will you?"
"... and you're alright with this?" he asked Ron.
"Its, erm, not either of your faults," said Ron, in a tone that made it clear he dearly wanted to lash out at someone, but wasn't clear on who. No matter what he said, though, Harry doubted he'd still be Ron's friend, if he slept with Lavender.
"Uh, can't I just, well, forgive the debt?" Harry asked.
Lavender shook her head. "Its a matter of honour, not money," she told him, "it doesn't work the same."
"Could I maybe transfer the debt to Ron?" he asked, grasping at straws a bit. "After all, I inherited it, so its not stuck to one person, right?"
Lavender looked thoughtful, an expression Harry found odd on her face. "Well," she said, finally, "I suppose if he won it from you, that would be honourable."
"Chess?" asked Harry, looking at his friend.
"Chess," said Ron, relieved.