The One With The Football - S3-E9
Trivia: During the football game, Phoebe's wearing a "That Girl" T-shirt with the signature caricature of Ann Marie (the lead on "That Girl" which aired on ABC), who was played by Marlo Thomas in the late 60's, and who also plays Rachel's mom, Sandra, in a few episodes.
The One With The Football - S3-E9
Trivia: In "TOW all the football" the two children on the swings in the background are the show's co-creater, Marta Kaufman's children.
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