I find these ghosts interesting... The ghosts in the previous Luigi's Mansion, the ones NOT Boos or portrait ghosts, were all creations of Van Gore. I wonder where these friendly ghosts came from.
I also have to wonder how King Boo escaped his portrait... Maybe Bowser took it or something... Either way, I also like how this pretty much establishes that King Boo is to Luigi as Bowser is to Mario. At least, that's how I see it.
And what's with that house Luigi's in? Did Mario kick him out of his house? Is that's what's left of his old mansion? Or did he just not collect enough money to fully rebuild it?