Hello forum,

I have been in a consistent gaming group for the last 3 years or so. Over that time, we have all been DM and players for campaigns of several different game systems, settings, and styles. One thing that is becoming increasingly common is the cameo appearance of a previous character or NPC, even if they switch setting(I.E. a Shadowrun NPC shows up in a high fantasy Pathfinder game). Overall, my group(as both players and DM's) have responded to these cameos with overwhelmingly positive feedback. Most of the time, these characters are present for one or two major scenes(~20 minutes real time), then they take an exit. I am currently the DM of our group, and some players are requesting cameos from previous campaigns(their old character, other PC's, and NPC's) and I am favoring adding in these characters at various times in the game. I also am prone to using famous real or fictitious people as NPC's for a cameo appearance.

My main question is how to make these the awesome Alfred Hitchcock, Quinton Tarentino, and Stan Lee style cameos without being shameless fan service or laziness in NPC design. I would also like to know if you even use cameo NPC's. If so, are they previous PC's of your own design? NPC's you made as a DM? PC's you played with? NPC's you saw as a PC? What about incorporating real or fictitious people into your game?

Thanks!