Personally, almost all of my random thoughts about RPGs can be filed under D&D, Encounter Critical or Traveller. That's just three systems, assuming you look at something like Mutant Future as a special case of the general field of D&D. Which I do. I'm curious if others get sudden inspirations about a wider range of games. Doc Rotwang! strikes me as being a likely candidate in this regard. Does anybody ever have unbidden thoughts about games they haven't played, read, discussed or otherwise thought about in years? I played one brief Shadowrun campaign when the game first came out and have never thought about it since unless someone us brought it up.
23 minutes ago