Almost all of my best RPG adventures and campaigns have come about largely by accident.
Tell me you haven't been here...
Imagine a snowstorm prevents most of your players from arriving for a game. Perhaps you realize you left your bag with your game books and materials home when you arrive at the game site. One day, Murphy's Law goes all 'Judge Dread' on you and nearly everyone has to cancel at the last possible moment. Have you ever woken up burned out and wanted to try something different for a change? Maybe you found a new game and asked your players, "Hey can we give this a shot? I just want to see how it plays." Maybe you've always wanted to try game X and as you sit down to play game Y the group says, "You know that game you've always wanted to play. We talked about it and we want to give it a go. Today."
Well all of these things have indeed happened to me and my response is to tell everyone who showed up to grab a piece of paper, write down some numbers and see what happens.
Recently, it just so happened that I came across the game InSpectres around the same time that I was getting ready for the next season of Ghost Hunters and Ghost Hunters International to start. Then I realized that it was the 25th Anniversary of Ghostbusters and a new video game had come out. All this literally clicked in my head within the span of two weeks.
Next thing I know, I'm contacting my friends and saying, "Hey would you guys like to try a Ghostbusters RPG one-shot?" The answer was yes and the one-shot went over much better than anticipated. For one thing, I mixed the humor of Ghostbusters with a downright sad and scary ghost story, directly tied into actual New Jersey folklore. I've never liked 'Horror RPGs' but a merging of horror, humor and mystery is very fun indeed.
The group is not of the 'Shoot first/Trap later' variety but instead tries to figure out why the ghost is still hanging around and then sees if they can help it move on. This quickly developed a unique identity to the team and its members and I saw more roleplaying in that 8 hour session then I sometimes see in any other 3 or 4 sessions with other games and groups. The second adventure had a heavy dose of action and proton blasting as the ghost in that scenario was bent on revenge.
All in all, a pretty awesome game that happened largely on a lark. I wish all my games could be like that but if I try to make them so...well then it wouldn't be accidental would it. Sigh.