There ain't nearly enough game threads on this forum, so let's start another one!
It's rather simple, really. You make up some story that sounds bad. The next person has to explain why the situation is fortunate, starting with "Fortunately,..." and the next person after that has to explain why it's unfortunate, starting with "Unfortunately,...". Repeat until thread dies, then start a whole new story.
For example:
I lost my shoe.
Fortunately, I have another one.
Unfortunately, it's too small.
Fortunately, I was able to find my first shoe.
Unfortunately, now I've lost the other one.
Fortunately, I decided to buy an entirely new pair.
You get the idea.
So, let us begin!

It's a rainy, gloomy-looking day today.

Fortunately,the dams need the water.

Are....you......actually starting to make decent posts?
I.....I'm not sure how to react.....

Unfortunately, the rain's so bad, that the dams are likely to overflow soon.

Fortunately,this is a very rare occurrence so the people are prepared to except a minor flood as long as the water restrictions are finally lifted.

Unfortunately, the flood won't be so minor. It'll be big enough to cover entire buildings.

Fortunately, the buildings need to be covered.

Unfortunately same buildings will be shaded from sun.

Fortunately, that will save on the expense of buying giant umbrellas.

Unfortunately, the giant umbrella industry collapses, bringing on a post-apocalyptic war where even the tiniest cocktail umbrellas are worth their weight in herring.

Unfortunately, right in the middle of the rain, a sudden wind will blow the covers off, costing more in repairs than the giant umbrellas would have cost.

Fortunately, the Puzzlemaster saw the double turns there and decided to start a new story.

The economy's about to collapse in Norway.

Fortunately, as a result of a rift in the space time continuum caused by the same time posts, time is rewound to before the flood occurred.
Oops! An even bigger rift in the space time continuum occurred.

Unfortunately, Norway has started to suffer extreme hyperinflation.

Fortunately, the U.N. has pitched in to improve the situation.

Unfortunately, the U.N. literally threw pitch on the situation.

Fortunately, the world market on pitch is quite strong, and due to the unforeseen pitch surplus Norway suddenly found itself having made them one of the worlds richest countries - and they started stockpiling Swiss cheese.