The One With The Triplets - S5-E3
Factual error: Joey always grabs his back when he gets his pain from his kidney stones. This is a classic referral pattern for pain when the stones are in the kidney. However, the doctor says that the kidney stones were too close to the bladder. Stones in the ureters classically refers the pain to the groin area. (00:02:40)
Answer: The statements that she's contradicting (that it is common, it happens to every guy, and it's not a big deal), are the things that a woman commonly says to a man who is suffering from erectile difficulty, typically to assuage his bruised ego. However, most men do not believe that these statements are true, as evidenced by Chandler's outburst. He's so caught up in the proof that women are lying about it that he gives himself away.
Rooster of Doom