Here is the joke.
It is a slow day in a little Greek Village. The rain is beating down and the streets are deserted.
Times are tough, everybody is in debt, and everybody lives on credit.
On this particular day a rich German tourist is driving through the village, stops at the local hotel and lays a 100 Euro note on the desk, telling the hotel owner he wants to inspect the rooms upstairs in order to pick one to spend the night. The owner gives him some keys and, as soon as the visitor has walked upstairs, the hotelier grabs the 100 Euro note and runs next door to pay his debt to the butcher. The butcher takes the 100 Euro note and runs down the street to repay his debt to the pig farmer. The pig farmer takes the note and heads off to pay his bill at the supplier of feed and fuel. The guy at the Farmers' Co-op takes the note and runs to pay his drinks bill at the tavern. The publican slips the money along to the local prostitute drinking at the bar; who has also been facing hard times and has had to offer him "services" on credit. The hooker then rushes to the hotel and pays off her room bill to the hotel owner with the note. The hotel proprietor then places the 100 Euro note back on the counter so the rich traveler will not suspect anything.
At that moment the traveler comes down the stairs, picks up the 100 Euro note, states that the rooms are not satisfactory, pockets the money, and leaves town.
No one produced anything. No one earned anything. However, the whole village is now out of debt and looking to the future with a lot more optimism.
Unfortunately, the joke is not related to the Greek crisis.
Here is a shorter version of the joke that is related to the Greek crisis.
Nobody in Greece has any debt. However, the Greeks would like to have more BMWs than they can afford with their income. They ask the Germans to lend them money to buy the BMWs. The Germans agree. The Germans ship the Greeks BMWs in return for pieces of paper signed by the Greeks promising that they will deliver enough money to enable the Germans to buy the same number of new BMWs back at a specified future date. In other words, the Greeks agree to provide the Germans BMWs in the future in return for the Germans providing BMWs for the Greeks now.
The repayment date arrives and the Greeks refuse to buy the Germans BMWs.
If this seems to complicated for you, consider your lending your car to your neighbor and then having him refuse to return it.