Phoebe can speak Italian to Joey's grandmother, but couldn't to Rachel's former lover, Paolo.
The Magna-Doodle shows the New York city skyline.
When Phoebe tells Rachel to check Chandler's jewellery box, she says "We have about 10 minutes, do you really want to get into that right now?" When she says this there are actually nearly 10 minutes left of the episode.
When Ross is speaking to Caitlin, in the background you can see the other cast members breaking character.
When Ross tries chatting up Caitlin, but keeps referring to bad-smelling gas, Chandler exclaims "Oh, the humanity!", which is a reference to the real-life 1937 airship disaster when the Hindenburg exploded, people jumped to their deaths, and the commentator, Herbert Morrison cried out "Oh, the humanity!"