The One With Phoebe's Dad - S2-E9
Corrected entry: After Ross breaks the radiator in the women's apartment, it gets so hot in there for their Christmas party that all the attendees strip down, some to their underwear. However, when Rachel answers the door to let a couple guests in, her nipples are erect, which would indicate the temperature inside is cold. (00:15:16)
The One With Phoebe's Dad - S2-E9
Corrected entry: When Phoebe is talking with her dad in Central Perk and he learns that her mom committed suicide years ago, he asks, "What about the girls?" He doesn't say anything, nor does Phoebe, about Frank, Jr., his son.
Correction: That's because Frank Jr. is his son with a different woman, who's still alive. Frank Jr. is Phoebe's half brother, remember. He's not worried about his son, only the girls, because they were left alone.
Correction: As most women - or those who spend time around women - could tell you, there's more than one reason a woman's nipples might be erect.