I have no idea how the universe-hopping works. XD I suspect it may be some kind of backwoods corner of the Kingdom Hearts universe because that's one of the few I can think of where crossovers are doable to this extent (and hey Sydney is a Squeenix character after all), but they haven't given me the details...
Glad you liked it! ^__^ I felt bad for making both of them have to be disappointed in who they were looking for, but the whole mistaken identity thing was just too tempting to let go...