It is nothing to do with halloween, it is to do with the gunpowder plot to blow up the English parliament, by Guy Fawkes in the year 1605, on the 5th of November.
The gunpowder plot failed and the event is celebrated with bonfires and fireworks every year in the UK.
One of the traditions is to make a model of Guy, from old clothes etc and go round asking for a 'penny for the guy' (probably should be a pound these days!) The pennies collected are traditionally used to buy foreworks for the celebration!
