Continuity: Across Series 3 - 5, Ross remains the same age (29) for all three years. In Series 3 he tells Chandler, "No thanks, I'm 29" when offered chocolate milk; in Series 4 when the guys try to party without Gandalf they all say they're 29; and in Series 5 when he's trying to reconcile with Emily, he says either he does, or he would get divorced for the second time before age 30.

Deliberate "mistake": The show is set in New York. Joey was a cast member on Days of Our Lives, which is filmed in Los Angeles, but is still always around.

Factual error: Phoebe's greatest love David leaves her to go to Minsk and comes and goes throughout the whole show, telling stories of Minsk on the way i.e. of the long months when the sun does not rise and the constant freezing cold. Minsk, being the capital of Belarus (although claimed to be in Russia for reasons explained in Corrections), is approximately as high up north as i.e. Wales and northern coast of Germany, and even during the winter months there is always daylight for several hours. Although winters in Eastern Europe are cold, the kind of coldness described by David would more believably happen in Siberia than Minsk, and the summers are just as nice and hot as everywhere in Europe.

Factual error: Chandler and Monica's wedding day is May 15th, as mentioned on the show. In Series 9, some time in January (as it is after the characters have celebrated Christmas and New Year), it is established that Rachel has been on maternity leave for five months, which means she took her leave in August. Since she realised she was pregnant in May the year before, this means her pregnancy lasted from April/May 2000 to August/September 2001, a time span of 16 to 17 months. This cannot be explained by saying that episodes don't have to take place in the month they air, as we are given the dates by the characters on the show.

Continuity: In S1 E1 a lady is seen walking past the window of Central Perk. In series 10 the same clip is used - everything's identical despite 10 years passing.

Continuity: The view from Monica's apartment changes after the first few episodes.

Continuity: Across the whole show, the infamous wall in Rachel's room / guest room (Monica's apartment) changes. When the room is not being filmed, the wall is as normal, but on quite a few episodes, when the room is actually used for scenes, the wall is much shorter. In both the episode where Ross buys Phoebe a bike, and where Phoebe and Rachel have to live with Monica after their apartment caught on fire, people are able to walk straight into the room without the wall being in the way.

Deliberate "mistake": The only time that any apartment doors are locked is when it is important to the episode. For example, Monica's apartment door is always unlocked, even when they go out or she and Chandler are having sex, but in The One Where Underdog Gets Away (Series 1), it's locked when there is all the "got the keys?" business. Also, Ross' apartment is never locked, except for in The One With Phoebe's Birthday Dinner (series 9), when they lock Emma in.

Continuity: Joey is shown moving into Chandler's apartment and meeting everyone for the first time approximately one year before Rachel showed up. It is also mentioned that it is a warm time of year, indicating that it is set during the summer months. However in 'The One with All the Thanksgivings' (series 6) Joey is shown living with the Friends by Thanksgiving (i.e. November) 1992.

Audio problem: Any scenes outside Central Perk always sound as if they're on a set (which let's be honest, they are) - the sound is often muted and footsteps on the pavement have a very slight echo to them.

Continuity: The Chick changes breeds and gender a couple of times. It starts out as a full size White Leghorn. During the adolescent phase it is a female White Silkie. This is a bantam or small size chicken. In maturity it is a male White Leghorn.