The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: While Joey's looking for the "hot girl" the second time, after he knocks on the little girl's door and asks if her mother, sister, or babysitter are a hot girl, he runs off when she shouts for her father, and when Joey stops in another hallway full of doors the shadow of the moving boom mic can be seen on the door beside him.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Rachel gets back from her first interview, just as Chandler says, "Oh hey," we can see the boom mic at the top of the screen.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Joey is standing at Monica's window waving to Ross, the end of the set wall with movement on the soundstage can be seen at the left side of the screen.

The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: After Monica tells Rachel that a guy from Ralph Lauren called and they want her for a second interview, when Rachel walks toward the TV and then when she stands in front of the TV, we can see a few tapes marks on the floor. One of those tape marks is also visible in one of Joey's closeups.
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