In season 1 of the show, James Michael Tyler was an unnamed extra working in Central Perk, the group's hangout spot. He earned his recurring role and name, Gunther, because he was the only one who could work the cappuccino machine.
The Magna-doodle in Chandler and Joey's apartment had different drawings and messages on it throughout the series that were apparently drawn by crewmember Paul Swain, who received no credit throughout the show. Most of them were inside jokes for the crew, but some were related to the show.
The big white dog in Joey and Chandler's apartment belonged to Jenniger Aniston. A friends gave it to her as a good luck gift when she got her role on the show.
Ellen Degeneres turned down the role of Phoebe.
David Schwimmer directed 10 Friends episodes, including the episode where the group finds out that ross is the father of Rachel's baby.
The triplets storyline was written for Lisa Kudrow to cover the real life pregnancy of her son Julian.
Some of the laughter from the show's live audience was cut in scenes so the next punch line wasn't lost.
In the episode "The One Where Everybody Finds Out," Phoebe and Chandler are playing a game of chicken over who will stop pretending to be into the other. Phoebe wants Chandler to admit he has been seeing Monica, and Chandler wants to keep that fact secret. To help advance the situation Joey pops Phoebe's shirt open with a quick hand movement and says, "it's not my first time." The live audience's laughter is so loud because it had actually taken him 12 takes to get it open.
In the first couple of episodes, Monica and Rachel’s apartment number was No. 5. This was changed in later episodes to No. 20 because the producers noted that 5 corresponded to an apartment on lower floor.
Lisa Kudrow had already been guest-starring on Mad about You as Ursula Buffay for two years before Friends aired. They decided to make Pheobe a twin to create a crossover between the two shows.
Here you have my two favorite episodes (which was very difficult to decide!)
The one with the unagi:
The one where Ross is fine:
Thanks for reading!