Dan: It's for a bio class, something with the human reproductive system.
Piper: You mean sex?
Dan: It's just too awkward for me to talk with my niece about.
Piper: Sure, not to worry I have plenty of experience.
Dan: Really! With sex.
Piper: No! I mean...talking about it. Yeh.
Lori Rom was originally cast as Phoebe but left the show after filming the pilot episode for personal reasons.