You're Bound to Win Halloween This Year With One of These Friends Costume Ideas

In "The One Where Everybody Finds Out," most of the gang finds out that Monica and Chandler are seeing each other, so they hatch a plot to get them to confess, which involves Phoebe trying to seduce Chandler until he breaks down.

What to wear: A royal blue dress with a matching lacy bra on display, along with one of Phoebe's signature updos.