Fungus?

[ffutures]

I recently re-read Raymond Briggs' Fungus the Bogeyman for a book club, and realised that it would make a wonderful RPG setting. I can't afford the rights etc. so can't publish anything, but I'd like to run an adventure for my own amusement. Unfortunately I need to come up with some ways to make the essential gloom and despair of the setting a fun experience for players, without subverting it by making everything too nice. The basic idea is a little too much like Monsters Inc. and I really don't want it to feel like that.

The plot would probably be something like the adventurers having to rescue another Bogeyman who has been captured by humans who think he's an alien, without revealing the existence of the underground Bogey homelands - it's a couple of months to the next con and I haven't firmed it up much as yet.

Not sure what rules system I'll use for this. Diana: Warrior Princess usually works OK for one-off games but tends a little too much towards flamboyance and humour, so it'll probably be Forgotten Futures or someone else's system. Modified Call of Cthulhu might work, with the Bogeys stealing SAN from the humans, but losing their own SAN if they are seen.

Any suggestions? Ideas for weird bogey-abilities? etc. etc.