The Friends cast have been joined by some famous faces over the years NBC

Twenty years ago this Monday (22 September) seminal sitcom Friends burst onto television screens with youth and charm in spades, blissfully unaware that they were about to help define a generation.

Even 10 years on from its final episode the show is still always on, repeated on numerous channels around the world to audiences old and new who even now are desperate for a full reunion of some kind (Jimmy Kimmel's half-reunion doesn't count).

We've already run down our favourite Ross Geller quotes, so now we're going to count down the 10 funniest guest appearances, and trust us when we say it was a very difficult list to put together. Arguments were had and friendships tested as the like of Bruce Willis, Jim Rash and Danny DeVito fell sadly short.

Before we get to the list, a quick disclaimer. In our opinion Tom Selleck (Richard), Paul Rudd (Mike Hannigan), Elliott Gould (Jack Geller) and Christina Pickles (Judy Geller) don't count because of the number of episodes they appeared in.

Here is our top 10...

10) Alec Baldwin

Famous New Yorker Alec Baldwin played one of a slew of famous faces to date Phoebe (Lisa Kudrow) over the years. Standing out over most, Baldwin plays Parker – a super-excitable, overly-enthusiastic man totally in love with life.

Best quote: "Well excuse me for putting a good spin on a traffic jam."

9) Charlie Sheen

Sheen played Ryan, a submarine commander on shore leave who doesn't have long to spend with Phoebe (another of her squeezes) only for them both to contract Chicken Pox at exactly the wrong time.

Best quote: "The lightning! The lightning was an unfortunate coincidence."

8) Tom Conti

Tom Conti played the father of Ross's (David Schwimmer) second wife Emily, and he makes it on this list despite limited screen time for a couple of cracking lines, but mainly because of the one below.

Best quote: "I could kill you with my thumb you know."

7) Christina Applegate

Each of Rachel's (Jennifer Aniston) two sisters appeared on the show but it's Amy, played by Christina Applegate, who was just a little funnier than Jill, played by Reese Witherspoon. Both played pretty awful people but Amy was worse, a big mess of hypocrisy blissfully unaware or uncaring of who she offends.

Best quote: Amy: "Like in Junior High, when you stole Timmy from me, I mean do you even realise how much that hurt me?"

Rachel: "Timmy was MY boyfriend, and YOU made out with him."

Amy: "Oh come on that was 20 years ago, get over it!"

6) Jon Lovitz

Lovitz appeared twice as the same character in season one as a stoned restaurateur and again in season nine going on a blind date with Rachel.

Best quote: "Oh cool, taco shells!"

5) Kathleen Turner

You'd have to be pretty brave to go up to Kathleen Turner and ask her to play the pre-op transsexual father of Chandler (Matthew Perry) but that's what one Friends casting director did, and we're very glad of it.

Best quote: "I'm not very fond of New York... Queens I like."

4) Gary Oldman

Oldman plays close to home as a celebrated actor called Richard Crosby who is starring opposite Joey (Matt LeBlanc) in a World War One movie around the time of Monica and Chandler's wedding. As the clock ticks down to their big day Joey needs to finish shooting as quickly as possible, only Crosby has other ideas turning up very, very drunk.

Best quote: "You wouldn't happen to have a very big fork?"

3) Hugh Laurie

The Friends characters are often accused of being terrible people and in one of our favourite guest cameos one of them gets torn down for being awful. Not many could get away with waltzing onto a popular show and getting away with pointing out how horrible a lead character is being, but Hugh Laurie gets away it beautifully.

Best quote: "Oh and by the way it seems to be perfectly clear that you were on a break."

2) Adam Goldberg

Not the biggest star name to appear on Friends, but without a doubt one of the show's most memorable guest characters. Goldberg played Eddie, Chandler's one-time roommate who took Joey's room after he briefly moved out. Absolutely insane – particularly about dried fruits – Chandler and Joey eventually conspire to force him out by making him believe he was never there in the first place.

Best quote: "You know what that is?... That's a tomato, this one definitely goes in the display."

1) Brad Pitt

The biggest name to guest on Friends is our pick for the funniest. Helped by having a whole episode written around his appearance, Pitt is excellent in helping those around him bring their A-game too. Making him an old friend of Ross who hates Rachel (played by his then-girlfriend Aniston) was a masterstroke.

Best quote: "That's right, we said your parents flipped a coin, decided to raise you as a girl, but you still had a hint of a penis."