After weeks of procrastinating, Rachel finally takes down the Christmas light on their balcony, only to fall off the balcony and sprain her ankle. At the hospital, Rachel - who has no insurance - cajoles Monica into trading identities so she can use Monica's coverage. When Ursula breaks Joey's heart Phoebe tries to fix it.
Trivia: Ursulla Buffay appears in many episodes after this one. As the same, unnice sister.
If you watch the shots between the two sisters and then in the later series, you can see that the camera work has seriously improved.