Your mum's the best shag in town

[Blondie]

Murphy, Collins and Vella are drinking in a pub when a drunk comes in,
staggers up to them, and points at Collins, shouting, "Your mum's the best shag in town!"

Everyone expects a fight, but Collins ignores him, so the drunk wanders off and stick his nose into a pint of Guinness at the far end of the bar.

Ten minutes later, the drunk comes back, points at Collins again, and says, "I just screwed your mum, and it was grand!"

Again Collins refuses to take the bait, and the drunk goes back to the far end of the bar.

Ten minutes later, he comes back and announces, "Your mum said it was the best thing since sliced bread!"

Finally Collins interrupts. "Go home, Dad,... you're pissed!"