Still harping on that Doctor Who RPG? Of course! I love it! It occurs to me that I could easily fold in material from other games into DW:AITAS if I were looking places and events to send the TARDIS to. Fantasy is pretty much out, though modern fantasy isn't impossible (there are vampires and werewolves in the Whoniverse, for example), and of course, superheroes shouldn't exist, but almost any kind of SF game can fit into the Whoniverse's future. Here then are the top 3 games I own that I could most easily fold into my DW:AITAS games and probably will.
Call of Cthulhu
The New Adventures and later book and audio series have already integrated the Lovecraftian Mythos into the Whoniverse. Who am I to argue? The only difference between CoC and Who scenarios is that the latter end with the heroes WINNING and probably banishing the Great OId Ones back to the depths of irreality. I'd love to do Time Lords versus Nyarlathotep stuff, but CoC also has some non-Mythos products (like Blood Brothers) that feature riffs on tons of horror movies (sound familiar?). CoC has the pulp, Edwardian feel of many Doctor Who episodes, alien-driven horror, investigation aplenty, people going insane, etc. It's a natural.
Key episodes: The Daemons, Image of the Fendhal, The Satan Pit.
Over the Edge
I may or may not ditch Al Amarja as a setting, but OTE is replete with mad science, weird characters, parasitic aliens, postmodern conspiracies and odd magics (no different than the Carrionites as far as I'm concerned). Mining it for ideas would be fun. Perhaps not too often because OTE tends to get disturbing in a Naked Lunch sort of way, but while I haven't read any OTE stuff in years, some of its images still stick with me. And I'm pretty sure I can 'port those memorable ideas to any kind of past or future setting for variety. I'd probably throw in some Unknown Armies stuff in there as well.
Key episodes: The Greatest Show in the Galaxy, Ghost Light, Midnight.
Well OF COURSE I was gonna say that. Not only because I'm a notorious GURPS head, but because of all those sourcebooks so compatible with time travel games! Want to go into the past? I'll recommend GURPS Vikings, Imperial Rome, Japan, Ice Age, Age of Napoleon, etc. Would rather travel to the future? GURPS Cyberpunk, Space, Age of Steel, Uplift, etc. all have interesting worlds to play with. The Horror books have an incredible amount of useful material suited to a Who campaign as well: Atomic Horror, Monsters, Cabal, Creatures of the Night, Weird War II... And who can't find good bits for a Who campaign in Place of Mystery, Cliffhangers, Villains, Warehouse 23, Timeline (in all the Time Travel stuff, actually), and plenty more. The great thing is, all the books are related, so each gives adventure seeds full of crossover potential. And in Doctor Who, you want an easy in to stick your peanut butter (alien monsters) into my chocolate (Dynastic China).
Key episodes: Practically all of them, but I'll name The Aztecs, Invasion of the Dinosaurs and The Unquiet Dead.
I feel all inspired now. What games would YOU fold into Who continuity?