The One With Rachel's Other Sister - S9-E8
Character mistake: While watching the parade near the beginning, Chandler gets excited because there's a band from Muskogee, OK, which is supposedly only four hours from Tulsa, where he works. It's actually less than an hour away from Tulsa.
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