I loved this collection of the published material from Greyhawk and comments from its players that Wayne R. published the other day.
It Was All Weird
Yeah, there are a lot of things that are silly, weird, and dangerous all at once.
Just about the only thing I haven't read from that list is the Bottle City - I missed that one, although I know about it.
Silly yet deadly is a really fun way to go. Greyhawk had Lewis Carroll levels, Diablo II had the Cow Level, so why shouldn't Felltower have something equally groan-inducing yet deadly?
I'm not interested in mixing sci-fi with my fantasy for my DF game, but I can promise some silly weird stuff is down in the dungeons, if you go deep enough, into the right cul-de-sacs, or play with the wrong doors or levers. Rich loot will also be in the weird spots, too - because you should remember plundering Wonderland or Monster Island with a grin.
Still, humor is a bit of a sensitive thing. I've run into "funny" encounters that just made me enjoy it all a bit less. So needless to say what I throw in will be aimed at what I think my players will find amusing but odd. But it is in there . . .