A guy walks into a bar, orders a pint and a pork pie, downs his pint, puts the pork pie on his head and smashes it with his hand, then walks out, leaving the barman a little confused.

The next day he comes back in, orders a pint and a pork pie, downs the pint, puts the pork pie on his head, smashes it with his hand and walks out, leaving the barman even more confused.

The next day he comes in again and orders a pint and a pork pie but the barman, trying to figure him out, says,"Sorry, no pork pies."

The guy orders a packet of cheese and onion crisps instead, downs the pint, puts the packet of cheese and onion crisps on his head smashes them with his hand and is about to leave when the barman stops him and asks, "Why did you just smash that packet of cheese and onion crisps on your head?"

The guy replies, "Because you didn't have any pork pies.”