Two men are playing golf when one realises he's left his jacket at the last tee

He goes back to get it, stops halfway and turns back. "What's up?" asks his mate. "Well, you see those two women at the tee. One's my wife, and she's playing with my mistress." His mate laughs and says, "No worries, I'll go get it for you." He stops halfway, comes back, looks at his mate and says "Small world."