Okay, so we have to wait a few weeks to see what Cassie's Harry will do in response to being smooched in that dark alleyway... so you may be wondering - what would other fandom Harrys do when smooched, out of the blue, in a dark alley, by Draco?
IP!Harry would say, "Stop toying with my feelings!" Then there would be 32 more chapters of angst.
LUW!Harry would say "Ma Nishtana!" (why is this night different from all other nights?" and snog him right back.
PoUniverse!Harry would use all his superspy moves, sort of like Keanu Reeves in The Matrix, then possibly decapitate him with his Mage powers, all the while yelling, "You seduced my then-girlfriend-to-be AND my ex-girlfriend and now you're after me too?"
Unlikely Coven!Harry: Hermione would slap Draco and send him back to John for more yoga lessons
TiP!Harry would pull away and say, "Oh, I always knew you wanted to do that. Hermione could tell years ago and warned me to be on the alert. I just didn't think you'd wait until after you were married."
PsychicSerpent!Harry's answer would be dependent on what universe they were in, although he'd always assume it was well within the realm of possibilities for any Draco.
AfterTheEnd!Harry would hit Draco with Rock #47. And there would be much rejoicing - not about the kiss, but about the hitting.
And if it happened in Surfeit of Curses...
Wait! I haven't finished the last chapter yet! How do you know it won't?
Any more hypothetical Fanfic!Harry Reactions?