Oh my God, this story FTW, man! This, this is why it is in my best interests to click on stories even if I don't normally read the pairing. (Nothing against the pairing, of course, just that there's only so many hours in a day, and many many pairings to read). ;) Anyway, this was FANTASTIC in all sorts of ways, starting with the very first line, which is also a compliment to the very premise/plot of the thing, which couldn't be more clever if it tried.
And Seamus? OH MY GOD, SEAMUS.
"Ron. You want Harry to admit that he's been shoving his tongue down your rabbit hole every few nights, aye?"
"And, Harry. You want Ron to believe that as tempting as his arse is, you have no memory of any tongue-spelunking into his nether-bits."
"Don't be wagging your tongue, Potter," Seamus says. "We all know where it's been."