(I found this on an Australian website but I guess it would apply around the world)

A guy walks into a pub on a quiet afternoon. The place is so quiet that he is the only customer.

He has a frightened manner about him. He approaches the bar and after looking around, he asks the barman to give him a shot of the house whisky "before the trouble starts".

The barman is a pleasant sort and after giving him an appraising look, sets him up.

The customer drains off the shot and asks the barman again: " Another one before the trouble starts".

The barman complies. Again the customer drains off the shot of whisky.

The customer looks even more frightened than he did when he came in. Again he looks around the empty bar and, again he asks the barman: "Another whisky before the trouble starts".

As the barman is pouring out the third whisky, he can't stop himself from asking: " "What is this trouble you're talking about?"

The customer drains off the third whisky.

The customer looks at the barman and says: " I haven't got any money".