The Magna-doodle on the door in the boys apartment has a different picture on it every episode. There is usually some tenuous connection between the picture and the plot of the episode.

Matthew Perry's wit is so legendary that the scriptwriters have often incorporated his gags into the show.

Jennifer Aniston's actual last name is Anastassakis but her family changed it to Aniston when they moved to the United States. If you watch TOW Chandler and Monica's Wedding, Jennifer's actual last name is used for the Greek couple having their wedding in the episode.

In the series 8 episode where Joey tells Rachel he loves her, the gay waiter in the restaurant is the same as the one in the series 9 episode with Phoebe and Joey's 'evil' plan. His name is Sam Pancake and he has worked in two Friends restaurants.

All the friends have a lot of expensive things in their apartments, but you have only seen them lock their doors twice.

The gold frame around the peephole in Monica and Chandler's apartment was originally the frame of a mirror, but was broken before filming began, and it was decided it should be kept anyway.

The artwork on the wall behind the couch in the coffee house changes every 6 episodes

In Friends, Joey is an actor on Days of our Lives, a program on which Jennifer Aniston's dad John Aniston plays Victor Kiriakis.

There is only one season where Janice never appears even once: the sixth (she does, however, make a pseudo-appearance when her voice pervades the mixed tape Chandler finds for Monica in the episode where they "make" each other Valentine's Day gifts).

The spare room (Rachel's) in Monica's apartment has a wall right opposite the door, which serves absolutely no purpose except to block the view into the room from the living room. The bedroom set isn't always built, just when needed, so having that wall makes life much easier. It's completely illogical though, as it's too thin to be a supporting wall, and where it is makes getting into the room a pain.

James Michael Tyler was just another extra at first, but since he was the only extra who knew how to use the cappuccino machine he got a bigger part as Gunther.

Phoebe's twin sister "Ursula" actually existed before Phoebe, as a character in another U.S. sitcom, Mad About You. In the first part of "The One With Two Parts," the two characters who come into Central Perk, thinking Phoebe is Ursula, are regular characters from that show.

Before the title "Friends" was settled, other titles considered for the show were "Friends Like Us," "Six of One," and "Across the Hall."

Rachel's sisters are called Jill and Amy. These are the same names as the co-producers of the show.

The opening sequence was recorded at 5am.

Many famous people are mentioned in the show and some end up guest starring! Two examples of this include Ross's List from Series 3, which includes Winona Ryder, who guest stars as Rachel's friend in Series 7. Also, Joey and Ross mention their favourite movie is Die Hard, and Bruce Willis guest stars in Series 6 as Ross's girlfriend's dad ("Hey, Mr. Stevens, you look like that guy out of Die Hard!").

They first put clips into the opening sequence in Episode 3, "TOW the thumb."

Another name that was considered for the show was "Insomnia Cafe."

The actress who plays the midwife in this episode goes on to play Joey's Agent, Estelle Leonard.

In the scene where Ross has just explained to Joey & Chandler that he has to give up Marcel, there is an advert break. Immediately after the break, the shot shows the three guys sitting on the sofa in the coffee house. If you look at the positions that their hands are in, they are mimicking either "See no evil", "Hear no evil" or "Speak no evil". I think this was done deliberately but since there isn't much laughter, I don't think the studio audience spotted it.