The One With Ross's Teeth - S6-E8
Monica: What happened to your teeth?
Ross: I whitened them.
Chandler: Really?
Ross: Yeah, what... What do you think?
Monica: Well, uh, I think I shouldn't look directly at them.
Ross: Come on, seriously.
Monica: Ross, they're really, really, really white!
Chandler: Yeah, what was wrong with your old... Human teeth?
Ross: Well, I did leave the gel on a little longer than it said to.
Monica: How much longer?
Ross: Uh, uh... A day.
Monica: Ross, you know that tonight is your date with Hillary?
Ross: I know! That's why I did it! Come on, are they really that bad?
Chandler: No. No, no, no, you'll be fine. Hilary's blind, right?
Monica: She will be after tonight.
The One Where Ross Dates a Student - S6-E18
Ross: I would date her, but there is a big age difference.
Joey: Well think about it - when you're 90...
Ross: I know, she'll be 80 and it won't be such a big difference.
Joey: No, that's not what I was going to say at all. What I was going to say is, when you're 90 you'll still have the memory of what it was like to be with a 20-year-old.
The One Where Ross Got High - S6-E9
Rachel: You guys, it was bananas, cream, and beef! I just cannot believe that you ate that so that I wouldn't feel bad.
Monica: Actually, I didn't eat mine. It's still in the bathroom.
Joey: No, it isn't. I ate that.
Judy: And we left ours in Monica's bedroom.
Joey: No. Got it, [nods to Jack] and got yours, too.
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