Sometimes, life likes to throw a monkey wrench into the cogs of a carefully laid-out plan. For example, tonight was supposed to be the first session of a new Pathfinder campaign. Unfortunately, two of the players couldn't make it do to some unforeseen circumstances (Which is fine. Sometimes shit happens) and since we didn't have enough people to run the adventure I had planned, the two players who did attend and I decided to go get some dinner and call it a night.
However, sometimes you don't want to just call it a night and go home without rolling some dice and having some fun with the few players that managed to show up. So, I started to think of a few things that I could do the next time this happens that will allow us to still have a game night and have some fun.
The first thing that came to mind was to have a back-up game ready to pull out at a moment's notice. For example, I've talked about how Superhero campaigns can be perfect back-up games before. Due to the nature of superheroes and the general power-level of a character in such a game, it is really easy to explain why certain characters are missing (they are out having their own adventures) and it's relatively easy to adjust to the smaller number of characters. I think Call of Cthulhu would work as well since I find it easier to run a game of Cthulhu with a smaller number of players.
Another option is to just play a game with a really simple or quick set-up and a story that can be made up pretty much on the fly. For example, I was trying to run a Dragon Age game at the beginning of the summer and the game just wasn't jiving that well with the group. So, we decided to switch things up and pulled out the old Jenga tower for a session of Dread. Everyone had a blast and it was easily one of the best gaming sessions I have had in a very long time. Also, depending on the amount of people you have at the table, you could also pull out Fiasco or Dungeon World and have some fun as well.
Finally, you could always go to the gaming closet and pull out a board game or card game. If you have a copy of it, Munchkin is perfect for this. Pandemic is also a good choice if you want a more cooperative game and Cards Against Humanity or one of the Flux's are excellent choices if you are in the mood for a card game.
While life likes to toss those curve balls at you occasionally, you don't have to let them affect you. Just try and roll with the punches and find another way to have some fun with your friends. It's why most of us do this in the first place.