Episode 92 of "Charmed"
s05e04 Siren Song
Title: Siren Song
Original Air Date: 10/06/2002 on WB
Director: Joel J. Feigenbaum
Writer: Krista Vernoff
Guest Stars: Amy Laughlin (Melissa), Hawthorne James (Demonic Healer), Branton Boxer (David), Greg Provance (Darklighter), Robert Merrill (Married Man), Tisha Gonsalves (Nurse), Tera Hendrickson (Simone), Daniel Betanles (TV Reporter)
Plot Outline:
Cole and Phoebe both fall under the spell of the Siren, who lures husbands to her and entrances their wives to follow with the intent to kill, leaving Piper and Paige to figure out how to save Phoebe. Piper, upset with Leo because he does not understand the challenges of being pregnant, and Leo, frustrated that Piper does not realize the demands of being a Whitelighter, have their personas switched magically by their unborn child.