On Friends season 1 episode 4, there is a scene where Monica, Phoebe, and Rachel are all on the balcony telling stories. At one point Rachel sits up from where she is leaning against a pillow on the fire escape and the pillow falls. Rachel takes a moment to let the audience laughter end and then says "anyway..." and tells her story.
Later, in the credits scene, a man knocks on the door of the apartment with an unamused look on his face, and without a word returns the pillow to Chandler who says thanks and sets it aside.
This seems like a mistake that was written into the episode after the fact to explain the falling pillow. Is this the case or was the joke originally intended to be in the episode?