Three are guys drinking in a bar, when another man comes in and starts drinking at the bar. After a while he approaches the guys, and, pointing at the one in the middle, shouts "I've fucked your mom!"

The three guys look bewildered as man resumes drinking at the bar.

Ten minutes later he comes back. "Your mom's sucked my cock!"

Same thing happens. Ten minutes later he announces "I've had your mom up the ass!"

The young guys have had enough, and the one in the middle stands up and shouts, "Look, Dad, you're drunk, go home!"