Supernatural (TV series)/Recap/S04/E14 Sex and Violence

Season 4, Episode 14:

Sex And Violence
Sam and Dean enter a small town in Iowa, where three men have inexplicably beaten their wives to death. The guys realize that behind the murders is a Siren, a creature that can take different forms and desperately needs love, compelling people to kill others or themselves as a show of devotion. The Siren eventually puts Sam and Dean under their spell and pits the two brothers against each other in a fight to the death.

Tropes

 * Disney Princess: The siren uses the names of Disney princesses when posing as a stripper.
 * Enthralling Siren
 * Impersonating an Officer: When another FBI agent questions the Winchesters' authority, they give him the number of their 'superior' to confirm who they are. Turns out, Bobby has a bank of phones in his home, each one used to impersonate a different agency (FBI, CDC, Homeland Security, etc).
 * Oh Crap: "Or she could be passing it through saliva."