"One day an Englishman, a" joke

One day an Englishman, a Scotsman, and an Irishman walked into a pub
together.
They each proceeded to buy a pint of Guinness. Just as they were
about to enjoy their creamy beverage, three flies landed into each of
their pints, and were stuck in the thick head.
The Englishman pushed his beer away from him in disgust.
The Scotsman fished the offending fly out of his beer and continued
drinking it as if nothing had happened.
The Irishman too, picked the fly out of his drink, held it out over
the beer and then started yelling "Spit it out, spit it out, you
bastard!"