Location: Kuwait Music: Jack Off Jill
I'm sure every game master or designer has, if for no other reason than to amuse himself (or his audience), planted a few Easter Eggs in his game. In the professional design world, I'm told it's a BIG "No, No" that can lead to all sorts of legal problems. You're not encouraged to base villains off coworkers (even when it's fun), to name spells or Feats after band songs, or to build encounters from your favorite movie. Inspiration is great and all, but if it evokes that, "I've heard/read/seen this before..." feeling in your audience, it's probably not a smart move.
Fortunately for me, I've got some pretty cool friends that are amused by the idea of being villains and heroes. I don't have to sweat the potential backlash that comes from turning them into nasferatu sorcerers, knights, or wandering skalds from Westholme. I don't have to worry about what they're going to say when I marry them off to their long term girlfriends or give them the pox (sometimes in both instances). I just get to write and have fun with it.
Of course, you need to show some restraint when you do. This isn't something you go wild with. You certainly don't populate your entire setting on your friends, either (which would start to approach weird in a big way). You have to be selective, and when you do act, let them discover those small gems. Or, if you share them, keep things small.
I think most people like being part of these things, especially when they appreciate the creative side of design work. They like to see the stats, see how you perceive them, and where you're willing to take them in a completely make-believe world. In short, it gratifies the ego.
But then again, so does designing and publishing your very own world....